Israel says it may broaden a ground assault that is says is aimed at destroying Hamas' network of cross-border tunnels, amid a land, sea and air offensive that has killed at least 294 Palestinians in the Gaza Strip.

For their part, diplomats have stepped up efforts to halt 11 days of bloodshed in and around Gaza while Pope Francis has demanded an immediate ceasefire in a phone call with Israeli President Shimon Peres and his Palestinian counterpart Mahmoud Abbas.

During talks on Friday in the Egyptian capital Cairo with Laurent Fabius, French foreign minister, Abbas reportedly sought French help to lobby Qatar and Turkey to pressure Hamas into accepting a truce.

In the face of Israel's military offensive, Hamas remains defiant, however, and has warned Israel it would "drown in the swamp of Gaza".

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

It was also announced that Ban Ki-moon, UN secretary-general, planned to travel to the Middle East on Saturday in an effort to end the hostilities.

Gaza health officials said more than 30 Palestinians have been killed since the launch of Israel's ground assault on Thursday, including three young siblings from the Abu Musallam family who were killed when a tank shell hit their home.

Earlier Benjamin Netanyahu, Israeli prime minister, said the military operation could yet be widened, despite growing international calls to avoid harm to civilians.

The Israeli offensive began on July 8 with the stated aim of stamping out cross-border rocket fire.

An Israeli civilian and a soldier have also been killed in the fighting so far.

Al Jazeera's Stefanie Dekker, reporting from Gaza, said Israeli troops were targeting the tunnels which Palestinian fighters were using.

"Hamas has managed to set up a tunnel - the Gaza under Gaza - which is a new thing that didn't exist in the last conflict," she said.

Reservists call-up

Early on Friday, Israel approved the call-up of another 18,000 reservists, taking the total number approved to 65,000, the army said.

The ground operation has sent thousands of people fleeing west to escape the fighting along the Israeli border, a UN official told AFP news agency.

"People are fleeing from east to west, away from the border," he said indicating that so far, about 30,000 people were taking refuge in 27 UN schools and other institutions.

By mid-morning Friday, the road between Gaza City and Khan Younis was deserted, with only a single minibus, packed with passengers, heading south, its windows covered with makeshift white flags, an AFP correspondent said.

Ebaa Rezeq, a Gaza City resident, told Al Jazeera that while Israeli soldiers remained near the buffer zone, air raids and shelling were continuing to terrify civilians.

During Friday prayers, imams at Gaza's 1,400 mosques relayed a single message to the faithful: "Be patient and strong. Victory will come."

With food supplies running desperately low, the World Food Programme said had already distributed emergency food rations and food vouchers to more than 20,000 displaced people since the conflict erupted on July 8.

But with the ground operation, it was gearing up for a huge increase in the coming days, Elisabeth Byrs, a WFP spokeswoman, said in Geneva, Switzerland.

Gaza was also struggling with a 70 percent power outage after electricity lines from Israel were damaged, officials said.

"We usually receive 120 MW and now it is zero," Fathi Sheikh Khalil, head of Gaza's electricity company, told AFP.

"We asked the Israeli electricity company to repair some lines on their side but they said it's too dangerous. Now 70 percent of the Gaza Strip is without electricity."

Network of tunnels

Israel has said the aim of its ground operation is to destroy Hamas's network of tunnels which are used for cross-border attacks on southern Israel.

On Thursday morning, 13 heavily armed fighters managed to infiltrate southern Israel before being spotted by troops, with one killed in an air strike and the rest fleeing back underground.

Israel pulled out all of its troops and settlers from Gaza in 2005, but within a year it became the de facto seat of Hamas after it won a landslide victory in Palestinian parliamentary elections.

Meanwhile, as Palestinian President Abbas headed to Turkey to further regional ceasefire efforts, Israel said it was pulling out some of its diplomatic staff following violent protests targeting the buildings of its embassy and consulate in Ankara and Istanbul.

Overnight, hundreds attacked the Israeli consulate in Istanbul in a violent show of anger, with police firing tear gas and water cannon at the protesters, an AFP correspondent said.

A similar number of protesters sought to break into the residence of the ambassador in Ankara, but police stood by and did nothing, another correspondent said.