Israel-Palestine conflict: Palestinian civilian toll mounts to 291; Hamas continues battle

Israel warned on Friday it could "significantly widen" a Gaza land offensive but was cautioned by its main ally, the United States, about the risks of further escalation as Palestinian civilian deaths mounted.

Palestinian officials said 58 Palestinians, at least 15 of them under the age of 18, have been killed since Israel sent ground forces on Thursday into the densely-populated enclave of 1.8 million Palestinians.

The Israeli military said it killed 17 Palestinian gunmen while another 13 surrendered and were taken for questioning after the infantry and tank assault began in the Islamist Hamas-dominated territory. 

In all, 291 Palestinians - most of them civilians, of whom at least 50 were under the age of 18 - have been killed since fighting began on July 8, Gaza officials said.​

One Israeli soldier was killed in an apparent fire incident, the military said, and several other troops were wounded in the ground operations. It said some 150 targets, including 21 concealed rocket launchers and four tunnels, have been attacked.

U.S. President Barack Obama said on Friday he had spoken to Prime Minister Benjamin Netanyahu, underscoring Washington's support for Israel to defend itself but raising concerns about "the risks of further escalation" and additional loss of innocent lives.

"We are hopeful that Israel will continue to approach this process in a way that minimises civilian casualties," Obama told reporters at the White House.

UN Secretary-General Ban Ki-moon planned to travel to the Middle East on Saturday in a bid to end the hostilities.

At an emergency session of the UN Security Council on Friday, UN political affairs chief Jeffrey Feltman condemned rocket fire into Israel but voiced alarm at "Israel's heavy response".

The Israeli land advance followed 10 days of barrages against Gaza from air and sea, hundreds of rockets fired by Hamas into Israel and failed attempts by Egypt, a broker of
ceasefires in previous Israeli-Palestinian flare-ups, to secure a truce.

"We chose to start this operation after we exhausted other options and reached the conclusion that without it we could pay a much higher price," Netanyahu told reporters before a special cabinet session at Tel Aviv military headquarters. "The main goal is to restore quiet. 

"My instructions to the Israeli army, with the approval of the security cabinet, is to prepare for the possibility of a widening, a significant widening of the ground operation."

He did not say what form a broadened offensive might take. Israel says its forces have focused so far on seeking out tunnels Palestinian militants might use for cross-border raids and moving weaponry. 

Gaza residents said Israeli forces has moved several hundreds metres (yards) into the north of the enclave and their deployment in the south of the territory was slightly deeper.  Hamas said its men were hitting Israeli tanks with mortar rounds and setting off bombs against troops crossing the sandy frontier under smokescreens.

To back up regular forces, Israel said it was calling up 18,000 military reservists, adding to 30,000 already mobilised. Abu Ubaida, spokesman for Hamas's armed wing, said it had thousands of fighters of its own "waiting to join the battle".

Hamas wants Israel and Egypt, whose military-backed government is at odds with the Palestinian Islamists, to lift border restrictions that have deepened Gaza's economic hardship and unemployment.

Israel last mounted a large-scale invasion of the Gaza Strip during a three-week war in late 2008 and early 2009 that claimed 1,400 Palestinian and 13 Israeli lives.