JERUSALEM (AFP) - - Three rockets fired from the Hamas-ruled Gaza Strip hit southern Israel on Tuesday, slightly wounding two people and straining an Egyptian-brokered truce between Israel and the Islamist movement.

Two of the rockets struck inside the hard-hit town of Sderot, causing some damage, and another struck a field outside town, police spokesman Micky Rosenfeld said.

The rockets were the first to be fired from the Palestinian territory since a truce between Israel and the Gaza Strip's Hamas rulers went into effect on June 19.

A spokesman for Islamic Jihad told AFP it had carried out the attacks. "The rockets are a response to the crimes of the (Israeli) occupation in the West Bank," he said.

The group, which was responsible for many of the attacks launched from Gaza in the months leading up to the ceasefire, did not agree to the truce but had vowed not to violate it.

The attacks came hours after Israeli troops killed a senior Islamic Jihad fighter and another man in the northern town of Nablus in the occupied West Bank, which was not included in the truce.

Overnight Tuesday a mortar round fired from northern Gaza hit Israel but caused no damage.

"Any fire from the Gaza Strip is a gross violation of the understanding reached with Egypt," Israeli Prime Minister Ehud Olmert's spokesman Mark Regev told AFP after the attack, referring to the truce agreement.

Hamas blamed Israel for Tuesday's violence, saying it had "provoked" Palestinian armed factions with the killing of the two men in Nablus.

"It is clear that it was the Israeli occupation that provoked the feelings of the Palestinian people and the resistance groups by committing these sorts of vile crimes in Nablus," Hamas spokesman Fawzi Barhum told AFP.

"We in Hamas affirm that we are adhering to the truce and working for its success and continuation and we will work with all the Palestinian factions to guarantee this."

Olmert, meanwhile, returned from Egypt where he met with President Hosni Mubarak on the truce and a parallel track of indirect talks with Hamas aimed at securing a prisoner swap for captured Israeli soldier Gilad Shalit.

Egypt played a key role as mediator in brokering the ceasefire as Israel rejects direct contact with Hamas, which it blacklists as a terrorist group. Hamas in turn refuses to recognise the Jewish state.

The truce, which called on Israel to cease all military operations in Gaza and for Palestinian militants to halt their near-daily rocket and mortar attacks, also called for the easing of a year-long blockade of the Gaza Strip.

Egypt told Israel that it will keep its Rafah crossing with Gaza closed until the fate of Shalit is resolved, a senior Israeli official said.

But Mubarak chided Israel, saying it was unrealistic to link Shalit's release to the truce.

To link the fate of "one soldier" to so many dead on both sides is "unrealistic," he said in an interview with Israeli television of which excerpts were published by the official MENA news agency.

"Let's be realistic and live the reality of the truce (or) they will continue firing rockets and you will attack them and you will die and they will die, for one soldier," Mubarak said.

"But the soldier is another track we're working on. Why mix everything up? Let's be realistic. We should not mix all issues and ruin everything" he said.

Israel has eased its year-old blockade of Gaza as part of the truce by allowing larger amounts of basic goods to enter, but made any opening of Rafah, the only crossing that bypasses it, conditional on Shalit's release.

Israel has also said it must keep up military operations in the West Bank to protect its citizens, and many feared an escalation in violence there could jeopardise the agreement.

Meanwhile, the international quartet for Middle East peace called during a Tuesday meeting in Berlin for the truce to "be respected in full."

"The quartet expressed its continuing support for Egyptian efforts to restore calm to Gaza and southern Israel and welcomed the period of calm that began on June 19," the grouping comprising the European Union, Russia, the United Nations and the United States said in a statement.

The statement also called for an immediate freeze to Jewish settlement activity in the occupied West Bank and the dismantlement of outposts built since March 2001.