Thousands of Israeli soldiers began a ground invasion into the Gaza Strip late Thursday, escalating a 10-day military operation that aims to destroy Hamas' offensive capabilities, including the group's weapons arsenal and tunnels that infiltrate Israel's territory.
The Israeli military said the operation was open-ended but limited in its scope, and would be carried out in several areas of the coastal strip.
The office of Israeli Prime Minister Benjamin Netanyahu said in a statement that the Israeli cabinet had approved the ground incursion, and that it came after Israeli forces stopped an attempted attack by 13 Hamas gunmen who tried to enter southern Israel through a tunnel earlier Thursday.
The statement said when Israel repelled the earlier incursion, it averted what it characterized as "a mass terrorist attack against Israeli civilians."
An Israeli military spokesman said Israel was not attempting to topple the Hamas Islamist group that rules Gaza. Such a move would likely require sending troops into densely populated Gaza City, resulting in urban warfare and huge casualty numbers for both sides.
The Gaza ground invasion came after 10 days of intense fighting between Israel and Hamas. Israel has carried out airstrikes on more than 2,000 targets in Gaza, and Hamas has launched more than 1,000 rockets at Israel.
Reuters witnesses and Gaza residents reported heavy artillery and naval shelling along the Gaza border. News reports said all power had been cut in Gaza City as of late Thursday.
Earlier in the day, a UN official said Israeli airstrikes on the Gaza Strip and Hamas rocket fire directed at Israel resumed after a five-hour humanitarian cease-fire expired Thursday. UN Humanitarian Coordinator for the Palestinian territories James Rawley said the truce was respected for the most part by all parties, but attacks resumed as soon as it expired.
"Rockets have been going out of Gaza and airstrikes and naval bombardment has resumed on Gaza," he said, "so once again the people of Gaza are suffering and probably dying, and the people of Israel are also being victimized by rockets and mortars going out of Gaza."
The streets of Gaza have been virtually deserted since Israeli military operations targeting Hamas began last week, as residents have stayed home or have sought protection at UN schools.
But for a brief time during Thursday's truce, Rawley said, citizens were able to go shopping or go to the bank, while some vital repairs were done to electrical and water facilities.
"It only was a pause of five hours, it was respected for the most part by all parties, which is good," he said, "but it is a pity that as soon as the pause is over, the hostilities have resumed."
U.S. State Department spokeswoman Jen Psaki asked Israel to redouble efforts to prevent civilian casualties. She described an attack that killed four Palestinian children playing on a Gaza beach as "horrifying."
Mourners in Gaza buried three of the Palestinian children Thursday. Israeli officials called the deaths "tragic" and said they were investigating.
U.S. Secretary of State John Kerry underscored in a telephone call with Netanyahu on Wednesday that "there's more that can be done" by Israel to avoid civilian casualties and that it must redouble its efforts, Psaki said.
But even while stepping up U.S. pressure for Israeli restraint, Psaki reasserted Washington's condemnation of Hamas's "indiscriminate rocket attacks" targeting Israeli civilians and affirmed U.S. support for Israel's right to defend itself.
More than 220 Palestinians have been killed in the conflict, while one Israeli citizen has died.
The U.N. agency for Palestinian refugees (UNRWA) reported 20 rockets were discovered hidden in a vacant school in Gaza. A statement from UNRWA said this was the first time weapons have been found in their facilities.
Meanwhile, talks for a broader truce are being held in Egypt, but Israeli and Hamas officials had backed away from earlier media reports that a deal had been reached.
Israel previously agreed to an Egyptian-backed deal that called for an immediate end to the fighting, the eventual easing of border restrictions and further talks hosted by Cairo.
Hamas rejected the deal, saying their leaders had not been consulted and it did not address other conditions such as Israel's long-standing blockade of Gaza.