At least 413 Palestinians have been killed, including 78 children, and 2,300 others wounded in Gaza since Saturday, the Palestinian Ministry of Health said.
Power cuts in the territory pose "a big challenge for the medical sector," the ministry said, threatening the lives of hundreds of others who need treatment.
Key context: Israeli Prime Minister Benjamin Netanyahu declared Saturday that Israel will halt the supply of "electricity, fuel and goods" into the Gaza Strip, although military spokesperson Lt. Col. Richard Hecht said Sunday only electricity had been cut.
Since then, power is only available for an average of four hours per day, down from the usual eight hours.
Israel has formally declared war on Hamas, which controls Gaza, after the militant group's surprise attack Saturday. It has been pounding the territory with airstrikes since.