Palestinian negotiators have warned they will leave Cairo on Sunday if their Israeli counterparts do not show up for truce talks, after Israel pummelled Gaza with fresh air strikes that killed at least 10 Palestinians.

Negotiations for a ceasefire in Gaza are expected to resume in Cairo on Sunday with an Israeli delegation scheduled to arrive in the city, where a Palestinian team and Egyptian mediators are waiting.

But an Israeli official told AFP that talks cannot take place until Palestinian rocket fire comes to a halt. Militants slammed 25 rockets into Israel on Saturday, amid mounting calls for a new ceasefire to halt fighting that has left nearly 2,000 Palestinians dead over the last month along with 67 on the Israeli side, mostly soldiers.

Two more rockets were fired at Israeli territory early Sunday, while the Israeli air force carried out 17 more raids, an army spokeswoman said.

Palestinian negotiators warned they would leave the Egyptian capital if no Israeli delegation showed up, with one senior Palestinian setting a 1300 GMT deadline.

"We have a meeting tomorrow (Sunday) with Egyptian (mediators). If we confirm that the Israeli delegation is placing conditions for its return, we will not accept any conditions," lead negotiator Azzam al-Ahmed told AFP.

Another senior Palestinian negotiator said they had given the Israeli delegation until 1300 GMT on Sunday.

Britain, France and Germany on Saturday urged Israel and Hamas -- the Islamist movement in de facto control of Gaza -- to agree to an immediate ceasefire.

A Hamas leader, Mussa Abu Marzuq, warned that the next 24 hours would be crucial.

Israel "is stalling and the next 24 hours will decide the fate of the negotiations", he said.

"We will not hold talks for a long time without serious discussions," he added overnight Saturday, calling Israel's attitude "not serious".

"We do not want an escalation, but we will not accept that there is no reply to our demands."

- Hamas-linked mosques destroyed -

The Cairo talks broke down on Friday after Hamas accused Israel of stalling and refused to extend a 72-hour ceasefire, setting off renewed hostilities that left 10 Palestinians dead on Saturday as Israeli warplanes battered Gaza with 50 air strikes.

The last month's fighting has devastated swathes of Gaza, with the United Nations saying at least 1,354 of the Palestinians killed have been civilians, including 447 children.

The Palestinian interior ministry said Israeli jets destroyed three mosques early Saturday. At least two of them were considered close to Hamas.

Gazan Ibrahim Taweel said the Israeli military telephoned him at 3:00 am, warning him to evacuate his nearby home five minutes before one of the mosques was attacked.

"I couldn't tell all my neighbours, so I evacuated myself and my neighbour and after five minutes an F-16 fired one rocket and after that a bigger rocket destroyed the mosque," he said.

The latest Palestinian rockets bring to 65 the number of projectiles launched at the Jewish state since the 72-hour truce ended on Friday morning, according to Israeli figures.

Israel says it has carried out more than 100 strikes in Gaza since Friday morning, targeting those responsible for the rocket fire.

- Protesters fill London and Cape Town -

Palestinian foreign minister Riyad al-Malki meanwhile said his government would soon try to haul Israelis before an international court for war crimes.

"We will go to the ICJ (International Court of Justice), and put our signature on it. Very soon we will be a (sovereign) state. That is enough for the court to start an investigation," Malki told AFP on a visit to Colombia.

In London, up to 150,000 protesters packed Oxford Street on Saturday, marching to the US embassy and on to Hyde Park, many of them chanting "Free, free Palestine" and holding up banners saying "UK -- Stop Arming Israel".

Tens of thousands of demonstrators also marched through Cape Town to protest the Israeli military operation, one of the biggest rallies in the city since the end of apartheid.

The lifting of Israel's land and sea blockade, imposed in 2006 after Hamas captured an Israeli soldier, has been a key demand of Hamas and the Palestinian Authority in the Cairo talks.

A Palestinian official said on condition of anonymity that Egypt and the Palestinians had reached a draft agreement for submission to Israel.

It would see Egypt and the Palestinian Authority take control of the Rafah border crossing into Egypt, essentially activating part of a unity accord Hamas signed with the PA in April.

Negotiations on the sea port, demanded by Hamas, would then be delayed and entrusted to the PA, with whom Israel is prepared to deal.

Israel waged the conflict to destroy Hamas's arsenal of rockets and its vast network of attack tunnels.

But combat has not resumed at the same fierce intensity, feeding hopes that a new truce could be agreed.

"Our hope is that the parties will agree to an extension of the ceasefire in the coming hours," US State Department spokeswoman Marie Harf said.

Chris Gunness, spokesman for the UN agency for Palestinian refugees (UNRWA), called for the Gaza blockade to end so reconstruction can begin.

"Huge swathes of Gaza have been levelled. We cannot rebuild it with our hands tied behind our backs," he said. "The blockade must end."

At least 65,000 people have had their homes destroyed, and UNRWA said 222,000 people are still sheltering in UN-run schools.