Palestinian hospitals have been overwhelmed by the number of injured

Palestinian deaths in the Gaza Strip have passed 1,000, medical sources in Gaza say, as Egypt continues efforts to broker a ceasefire.

Nearly a third of the dead are reported to be children and nearly 5,000 people have been injured.

UN Secretary General Ban Ki-moon said he wanted to find a durable and sustainable ceasefire between Israel and Palestinian fighters.

But clashes reportedly intensified as Mr Ban began a Middle East tour.

The Ministry of Health in Gaza said 1,013 people have died in the conflict which started 19 days ago.

More than 300 of the dead are said to be children, 76 are women and more than 4,500 people have been injured, of whom 1,600 are children and 678 are women.

Thirteen Israelis have been killed, including three civilians and one soldier from rockets fired from Gaza and nine soldiers killed in fighting in Gaza.

It is impossible to independently confirm casualty figures as Israel has refused to allow international journalists to enter Gaza.

Diplomatic push

Egypt has been leading efforts to broker a ceasefire, that could include a new force of peacekeepers to prevent smuggling on its border with Gaza.

Ban Ki-moon, speaking after talks in Cairo with President Hosni Mubarak, said he hoped the Egyptian initiative would show results as soon as possible.

The UN secretary general next goes on to Israel, Jordan, the West Bank and Syria.

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Also on Wednesday, Hamas officials were in Cairo speaking to Egyptian negotiators.

After the talks, a senior Hamas political leader told the BBC's Rushdie Aboualaf in Gaza that the Egyptian initiative had been positively received but that more time was needed to discuss it.

Hamas, which controls Gaza, has said any ceasefire agreement would have to entail a halt to Israeli attacks, a complete withdrawal of Israeli forces and the opening of border crossings to end the blockade of Gaza.

BBC Arab affairs analyst Magdi Abdelhadi says the gap between Israel and Hamas appears to be as wide as ever.

Israel will not agree to a deal that does not guarantee an end to Hamas's smuggling of weapons across the Egyptian border and the cessation of rocket attacks into southern Israel.

For its part, Hamas refuses to accept an agreement that could in effect spell the beginning of the end for its military wing.

Egypt and other key Arab states can put pressure on Hamas but the US remains unwilling to press Israel to make any concessions, our correspondent says.

A senior Israeli defence official, Amos Gilad, is to travel to Cairo on Thursday for talks with Egyptian negotiators, a spokesman for Israeli Prime Minister Ehud Olmert said.

'Seeds of extremism'

Israel launched its campaign against Gaza on 27 December, saying it wanted to end Palestinian rocket fire into Israel.

The Israeli foreign ministry has said there is no guarantee Hamas would respect any ceasefire agreement.

Both Hamas and Israel rejected last week's UN Security Council resolution calling for an immediate ceasefire.

The Israeli offensive has provoked widespread international condemnation at the cost in civilian casualties.

Bolivian President Evo Morales said he was cutting relations with Israel over what he called the "genocide" in Gaza.

President Bashar al-Assad of Syria warned that Israel's campaign would fuel extremism and terrorism in the Arab and Muslim world.

"The effect of war is more dangerous than war. It is sowing seeds of extremism around the region," Mr Assad said in an exclusive BBC interview.

Israeli divisions?

On Wednesday, residents spoke of heavy machine-gun fire as Israeli troops fought Hamas gunmen near Gaza City.

Israel continued to bombard the Gaza Strip after launching 60 air strikes overnight, which officials said targeted weapons-smuggling tunnels under the border to Egypt and a cemetery in Gaza City which was claimed to be a rocket-launching site.

Meanwhile, three rockets were fired from southern Lebanon towards the northern Israeli city of Kiryat Shmona, landing on open ground.

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No casualties or damage were reported.

Analysts say Israel may be holding back from all-out urban warfare in Gaza City, something that would cause heavy casualties on both sides and be politically risky less than a month before Israel holds elections.

Israeli media has reported divisions within the government, with Defence Minister Ehud Barak said to favour a week-long ceasefire..

But Prime Minister Ehud Olmert says he wants to press on with the military campaign for however long it takes, reports say.

In another development, a newly-released audiotape said to feature the voice of al-Qaeda leader Osama bin Laden has called for a holy war to stop the Israeli offensive in Gaza.

The authenticity of the tape, posted on a number of Islamic militant websites, could not be independently verified.