Israeli warplanes carried out 30 air strikes over Gaza on Saturday, killing five Palestinians, as fighters fired six rockets into Israel, leaving international mediators scrambling to rescue ceasefire talks.

Gaza emergency services said two men were killed in a strike on a motorcycle in Al-Maghazi camp and that the bodies of three others were pulled from the rubble of the Al-Qassam mosque in the Nuseirat camp in the middle of the enclave.

The Palestinian interior ministry said Israeli jets destroyed three mosques, the one in Nuseirat, one in the Zeitoun area and one in Jabaliya in the north.

At least two of the mosques were considered close to Hamas.

Only the minaret was left standing at the huge Al-Qassam mosque, an AFP photographer said.

"We heard a loud explosion and it was the beginning of the explosions and a warning to residents to evacuate the area to stay away," said Jood Irhaem, who lives close to one of the mosques.

"Minutes later there were two strong explosions."

Israel said Palestinian fighters fired six rockets into Israel on Saturday, bringing to 44 the number of projectiles launched into the Jewish state since the end of a 72-hour truce on Friday.

One civilian and a soldier were wounded on Friday, but no injuries or damage were reported on Saturday.

Israel said it had carried out around 100 strikes in Gaza since Friday, 30 of them since midnight.

Palestinian medics say 10 people have been killed and more than 40 wounded since the truce expired.

In the occupied West bank, two Palestinian men died after being shot by Israeli troops during violent clashes at protests in Hebron and near the Jewish settlement of Psagot, medics said.

The month-long conflict flared again after mediators tried but failed to extend a ceasefire that expired on Friday morning as Palestinian fighters shattered the quiet with pre-dawn rocket attacks.

Fighting between Israel and Hamas has now killed at least 1,900 Palestinians and 67 people on the Israeli side, almost all soldiers, since July 8.

The United Nations says at least 1,354 of the Palestinians killed since July 8 were civilians, including 447 children.


'Egypt, US still trying'

Many Palestinians who had gone home during the ceasefire have returned to schools. Adnan Abu Hasna, a spokesman for the UN agency for Palestinian refugees, said 222,000 people we sheltering in 89 UN schools.

But combat has not resumed with the same fierce intensity, feeding hopes for a new truce.

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

Acting US Middle East peace envoy Frank Lowenstein, in Cairo for some days, "is still trying to help the parties get a permanent ceasefire," a US embassy official said.

Egyptian mediators met a Palestinian delegation again Friday evening and were waiting to hear back from the Israelis after Shabbat, the Jewish sabbath, ends at sundown Saturday.

Israel warned it would not negotiate under fire, and Prime Minister Benjamin Netanyahu ordered the military to retaliate "forcefully" and blamed the Islamist movement Hamas for breaching the ceasefire.

In southern Israel, the army has banned gatherings larger than 500 people within 40 kilometres (25 miles) of Gaza, and said kindergarten and summer camps could only operate if there was a bomb shelter nearby.

Pressure group Peace Now has called on supporters to rally on Saturday night in Tel Aviv against the war and to call for a diplomatic solution.


'Bibi too strong': Obama

President Barack Obama told The New York Times in an interview published Saturday that there were limits to US influence on both sides to reach a solution to the decades old Israeli-Palestinian conflict.

Netanyahu had a strong support base in Israel and Palestinian president Mahmud Abbas was weak domestically, he said.

"If he (Netanyahu) doesn't feel some internal pressure, then it's hard to see him being able to make some very difficult compromises, including taking on the settler movement," Obama was quoted as saying.

"In some ways, Bibi is too strong (and) in some ways Abu Mazen is too weak to bring them together."

Hamas and Palestine Liberation Organisation officials want the lifting of Israel's eight-year blockade of Gaza and the building of a sea port.

They also want Israel to free 125 key prisoners.

A British, French and German proposal to rebuild Gaza aims to strengthen the hand of Abbas and his Palestinian Authority while clamping down on Hamas and other Gaza fighters to ensure Israel's security.

Israel waged the conflict to destroy Hamas's arsenal of rockets and its network of attack tunnels that posed a direct threat to the Jewish state.