This picture shows flares dropped by Israeli forces above the Palestinian enclave. AFP

Israel on Monday pounded Gaza with "significant" strikes with soldiers battling Hamas forces in the besieged territory, ignoring ceasefire calls by UN aid agencies who condemned surging civilian deaths in the month-long conflict.

Israeli troops and Hamas fighters engaged in house-to-house combat in densely populated Gaza, where the war has sent 1.5 million people fleeing to other parts of the territory in a desperate search for cover.

The health ministry in Gaza, which is run by Hamas, says more than 9,770 people, mostly civilians, have been killed in Israeli strikes and the intensifying ground campaign since the war began.

"We are striking Hamas, and we are going stronghold after stronghold, according to our plan, in a systematic effort to dismantle Hamas from its military capabilities," Israeli army spokesman Jonathan Conricus told CNN.

"We have troops on the ground; infantry, armour, combat engineers. They are striking and they are also directing fire from the air," he said, adding efforts were focused on the "underground infrastructure" network of Hamas tunnels.

This handout picture shows Israeli tanks and soldiers stationed at a location in the northern Gaza Strip. AFP

"This strike is like an earthquake," Gaza City resident Alaa Abu Hasera said, in a devastated area where entire blocks were reduced to rubble.

Israel launched a massive bombing campaign on the Hamas-ruled Gaza Strip after the Palestinian Hamas group staged the worst attack in Israel's history.

'Enough is enough'

Israel has distributed leaflets and sent text messages ordering Palestinian civilians in northern Gaza to head south, but a US official said Saturday at least 350,000 civilians remained in what is now an urban war zone.

On Sunday, the health ministry said 45 people were killed in Israeli strikes on a refugee camp in central Gaza, leaving survivors desperately searching through the rubble.

"Are there any survivors?" shouted Said Al Najma, as he tried to shift the blocks of concrete strewn across the road in the camp.

"They brought down an entire street on the heads of women and children without any notice," he said.

Palestinians inspect the damage of a destroyed house following an Israeli airstrike in Jabaliya refugee camp. AP

Deepening the desperation in the crowded territory, the sole border crossing into Egypt was closed Sunday for a second day in a row, with Hamas suspending the evacuation of foreign passport holders after Israel refused to allow some injured Palestinians to be evacuated.

The UN Office for the Coordination of Humanitarian Affairs (OCHA) confirmed the closure, saying more than 1,100 people had been allowed out in the two days previous.

The Israeli army has encircled Gaza City, effectively splitting the territory in two, with "significant" strikes carried out, army spokesman Daniel Hagari said late Sunday.

Shortly before the strikes, internet and telephone lines were cut, and the strikes would continue overnight and in the days to come, Hagari added.

Since Israel sent ground forces into the north of Gaza late last month, "over 2,500 terror targets have been struck" by "ground, air and naval forces", the army said Sunday.

The fighting comes as US Secretary of State Antony Blinken presses a whirlwind Middle East tour focused on humanitarian aid for the Palestinians, that has taken him to Israel and the occupied West Bank, as well as to Jordan, Iraq and Cyprus.

Blinken, who has rebuffed calls for a ceasefire and backed Israel's goal of crushing Hamas, met Sunday with Palestinian president Mahmud Abbas in the West Bank.

Palestinians search for casualties at the site of Israeli strikes on houses in central Gaza Strip on Sunday. Reuters

Abbas denounced "the genocide and destruction suffered by our Palestinian people in Gaza at the hands of Israel's war machine, with no regard for the principles of international law," the official Palestinian news agency Wafa said.

The war has exacerbated tensions in the West Bank, where more than 150 Palestinians have been killed in clashes with Israeli forces and in settlers since the start of the war, according to the Palestinian health ministry.

As concern grows at mounting casualties, the heads of all major United Nations agencies issued a joint statement expressing outrage at the civilian death toll in Gaza and calling for an "immediate humanitarian ceasefire".

"For almost a month, the world has been watching the unfolding situation in Israel and the Occupied Palestinian Territory in shock and horror at the spiralling numbers of lives lost and torn apart," the UN chiefs said, including the heads of UNICEF, the World Food Programme and the World Health Organization.

"We need an immediate humanitarian ceasefire. It's been 30 days. Enough is enough. This must stop now."

Agence France-Presse