The Iran-backed Houthi rebels say they "will meet escalation with escalation" after the US and UK struck at least 36 Houthi targets at several locations in Yemen on Saturday.

The strikes mark a second day of major US operations against Iran-linked militia groups in the Middle East.

Here's what you need to know...

US and UK strikes

Saturday's attack: The US and UK with the support of other countries "specifically targeted sites associated with the Houthis' deeply buried weapons storage facilities, missile systems and launchers, air defense systems, and radars,” according to a joint statement. They said their "aim remains to de-escalate tensions and restore stability in the Red Sea," where the Houthis have been attacking shipping.

Houthis vow to retaliate: In response to the strikes, Mohammed Al Bukhaiti, a member of the Houthi Political Council, wrote on X Saturday that the "American-British aggression against Yemen will not go unanswered," adding that the Houthis's "military operations against Israel will continue until the crimes of genocide in Gaza are stopped."

Houthis had "repeated warnings": On Sunday, British Foreign Secretary David Cameron said the strikes were carried out after "repeated warnings" were issued to the Houthis, whose attacks "must stop." He added that their "reckless actions are putting innocent lives at risk, threatening the freedom of navigation and destabilising the region."

Political solution "difficult": The strikes in Yemen come a day after the US hit at least 85 targets associated with pro-Iranian militia groups in Iraq and Syria in response to a drone strike that killed three American soldiers in Jordan. Iranian Foreign Minister Hossein Amir-Abdollahian said recent strikes by the US in the Middle East, and its decision to designate the Houthis as a terrorist organization, have "complicated the situation and made it more difficult to reach a political solution," according to the state news agency, IRNA.

Gaza conflict

Palestinian death toll rises: Israeli attacks have killed at least 127 people and injured 178 others in Gaza over the past 24 hours, the Hamas-controlled Palestinian Ministry of Health in the strip said Sunday. It added that altogether 27,365 Palestinians had been killed and 66,630 injured in Gaza since October 7.

Biden not giving war "full backing": Israel’s far-right National Security Minister Itamar Ben Gvir told the Wall Street Journal on Sunday that US President Joe Biden is not giving Israel his "full backing" in its war against Hamas. Benny Gantz, a former defense minister and a member of Israel’s war cabinet, called his comments "irresponsible" and urged Israeli Prime Minister Benjamin Netanyahu to “call (him) to order.”

Thousands protest in Israel: For the third weekend in a row, thousands of people took part in demonstrations in parts of Israel on Saturday to demand a change in government and the release of the remaining Israeli hostages in Gaza. Some say the government's actions show that "its citizens are not at the top of its mind,” as anger over Netanyahu’s handling of the hostage crisis rises.

Thousands of Hezbollah targets hit: The Israeli Defense Forces says it has attacked more than 3,400 Hezbollah targets in southern Lebanon and more than 50 in Syria since the war in Gaza broke out on October 7. Spokesperson Daniel Hagari said the aim is to stop Hezbollah's “supply chain of ammunition and missiles” being smuggled from Iran to Syria and then to Lebanon.

The US and UK have conducted strikes on Houthi targets in Yemen with the support of several other countries, hitting at least 30 targets across at least 10 locations, according to officials.

The strikes in Yemen follow Houthi attacks on international shipping lanes and US warships in the Red Sea which the Houthis say are in response to Israel's war in Gaza.

Here's what you need to know about the group:

The Houthi movement, also known as Ansar Allah (Supporters of God), emerged in the 1990s and is one side of the Yemeni civil war that has raged for nearly a decade – a conflict that spiraled into a wider war in 2015 when a Saudi-led coalition intervened in an attempt to beat back the Houthis.

Eight years later, the Houthis remain in control of much of Yemen, particularly in the north. .

The group are believed to have been funded, armed and trained by Iran, and form part of Iran’s so-called “Axis of Resistance” – an anti-Israel and anti-Western alliance of regional militias backed by the Islamic Republic.

The Shiite-Muslim Houthis are now seen in parts of the largely-Sunni Muslim world and beyond as champions of the Palestinian cause.

While the Palestinian cause has always been central to Houthi ideology, experts say their actions in the Red Sea come with other benefits, such as projecting their power beyond Yemen.

You can read more on the Houthis here.

Israeli attacks have killed at least 127 people and injured 178 others in Gaza over the past 24 hours, the Hamas-controlled Palestinian Ministry of Health in the strip said Sunday.

CNN cannot independently verify the number of casualties on the ground.

The health ministry added that altogether 27,365 Palestinians had been killed and 66,630 injured in Gaza since October 7.

As of January 8, according to Palestinian statistics, about one in every 100 people in Gaza had been killed since the war between Israel and Hamas erupted.

Israel believes that it has killed two Palestinian civilians for every Hamas militant in its intense campaign to eliminate the armed group from the Gaza Strip, a ratio an IDF spokesperson described to CNN last month as “tremendously positive.”

More than 1,200 people were killed and some 200 others were kidnapped in the October 7 terror attack in southern Israel. Some 130 hostages remain in Gaza.

British Foreign Secretary David Cameron said Sunday that the UK and US carried out strikes on Houthi military targets after "repeated warnings" to the Iran-backed group. 

"The UK and the US have carried out further strikes on Houthi military targets," Cameron said in a statement posted on X, adding: "We have issued repeated warnings to the Houthis."

"Their reckless actions are putting innocent lives at risk, threatening the freedom of navigation and destabilising the region," Cameron continued.

"The Houthi attacks must stop," he wrote. 

Saturday's strikes in Yemen: The US and UK conducted strikes with the support of several other countries on at least 30 Houthi targets across 13 locations in Yemen from air and surface platforms, according to officials. 

In a joint statement with Australia, Bahrain, Canada, Denmark, the Netherlands and New Zealand released Saturday, they said: "Our aim remains to de-escalate tensions and restore stability in the Red Sea."

Mohammed Al Bukhaiti, a top member of the Houthi Political Council, warned on X Saturday that the Houthis "will meet escalation with escalation," and will continue their military operations against Israel "until the crimes of genocide in Gaza are stopped."

US President Joe Biden is not fully supporting Israel’s goals in its war against Hamas in the Gaza Strip, Israel’s far-right National Security Minister Itamar Ben Gvir told the Wall Street Journal.

“If Trump was in power, the US conduct would be completely different," Ben Gvir, head of the nationalistic Jewish Power party, added.

Benny Gantz, a former defense minister and a member of Israel’s war cabinet, hit back at Ben Gvir, calling his comments “irresponsible” in a post on X and urging Netanyahu to “call (him) to order.”

"It is permissible to have disputes, even with our largest and most important ally (the United States), but they must be conducted in the relevant forums and not in irresponsible statements in the media, which harm the strategic relations of the State of Israel, the security of the state, and the war effort at this time,” he said.

Netanyahu is under pressure from all sides, as disputes in his coalition and war cabinet threaten to bring the government to a breaking point, and large rallies across the country are demanding he step down and send the country to an election.

Thousands of people protested in parts of Israel on Saturday to demand a change in government and the release of the remaining Israeli hostages in Gaza.

In the coastal town of Caesarea, protesters rallied in the rain before marching toward one of the private residences of Prime Minister Benjamin Netanyahu.

In Tel Aviv, protesters gathered at Habima Square to call for immediate elections in what was the third weekend in a row of demonstrations directly targeting Netanyahu and his government.

Many waved Israeli flags and held up signs with images of the Israeli hostages, calling on the government to “bring them home.”

“We will go out to demonstrate that our future depends only on us - we the people will determine our destiny!,” the said. 

Pressure mounts: With more protests scheduled for next Saturday, the demonstrations are becoming a regular occurrence.

Last Spring and Summer, mass weekly protests against Netanyahu and his government occurred over planned judicial reform, but were put on hold after the brutal October 7 attack. With the anger over Netanyahu’s handling of the hostage crisis rising, such demonstrations could soon be returning.

The US and the United Kingdom have conducted strikes on Houthi targets in Yemen from air and surface platforms — including F/A-18s — on over 30 targets across 13 locations, according to officials.

The US and UK carried out the strikes with the support of several other countries, according to a joint statement on Saturday.

The Houthis said US and UK warplanes struck multiple provinces in Yemen, including the capital of Sanaa.

Two US destroyers fired Tomahawk missiles as part of the strikes, a US official told CNN. The USS Gravely and USS Carney fired the land-attack cruise missiles and F/A-18 fighter jets from the USS Dwight D. Eisenhower aircraft carrier were also involved, officials said.

For context: Strikes on consecutive days come as President Joe Biden's administration has vowed a “multi-tiered” response to a drone attack that killed three US service members and wounded more than 40 last weekend.

Seeking to avoid a regional war with Tehran, the US has not targeted Iran directly, instead going after some of its most powerful proxies in the region. It is an indirect way of trying to send a message to Iran’s leadership, which has grown increasingly nervous about the actions of some of the militant organizations it backs, CNN has reported. Iran funds, arms and supplies these groups to different degrees, but its leadership does not control them directly.

The strikes in Yemen are distinct from the attacks in Iraq and Syria: The former is a response to ongoing Houthi attacks on international shipping lanes and US warships in the Red Sea, while the latter is a retaliation for a deadly attack on US troops. But both target Iranian-backed groups in the Middle East.

CNN's Eyad Kourdi contributed to this post.

US forces struck an additional Houthi anti-ship cruise missile in Yemen early Sunday local time, according to US Central Command.

The strike was conducted in "self defense" against a Houthi cruise missile "prepared to launch against ships in the Red Sea" at 4 a.m. local time on Sunday, US Central Command said in a statement. 

US forces determined the cruise missile presented an "imminent threat" to US Navy ships and other vessels in the region.

The strike is a part of the US military's effort to deter the Houthis from further disrupting the global shipping lanes in the Red Sea. 

Israel’s military has attacked more than 3,400 Hezbollah targets in southern Lebanon and more than 50 in Syria since the war in Gaza broke out 120 days ago, Israel Defense Forces spokesperson Daniel Hagari said.

At a press briefing Saturday, Hagari said Israel has been trying to stop Hezbollah's “supply chain of ammunition and missiles,” which he alleged were being smuggled from Iran to Syria and then to Lebanon.

Hagari also said the Israeli military has deployed three divisions along the Lebanese border since October 7 -- instead of the usual single division to try to thwart Hezbollah's capabilities and protect people in northern Israel.

Hezbollah on Saturday said it had launched at least eight attacks on Israeli positions.

The IDF acknowledged that “a number of launches” were identified crossing from Lebanon to northern Israel, but said no injuries were reported and that it struck the sources of the fire.