Ahmed Qureia, the Palestinian Prime Minister, was forced to cut short a visit to the West Bank city of Nablus today after gunmen unleashed a volley of shots towards the building were he was holding talks, underlining the growing state of lawlessness.

Even as the Prime Minister’s bodyguards hustled him away from the sports club in the city’s Balata refugee camp, militants fired further shots and a bomb exploded some distance from his motorcade, although there were no injuries.

The protest by disgruntled militants further highlighted the uphill task facing Mahmoud Abbas, the Palestinian President, as he attempts to rein in militants just a day after a summit with Ariel Sharon, the Israeli Prime Minister, ended in deadlock, leaving the four-month ceasefire in a precarious state.

Israel, angered by an upsurge in violence, had given the Palestinians few concessions and turned the screw further today when it confirmed it had resumed a policy of targeted assassinations of senior militants, a measure it had confined only to activists caught breaking the ceasefire declared during February’s Sharm el-Sheikh summit.

While Mr Abbas and Mr Sharon conducted their two-hour meeting at the Prime Minister’s official residence in Jerusalem yesterday, the Israeli air force fired a missile into a building in Gaza in a fruitless attempt to kill an Islamic Jihad commander.

"There was an attempt in Gaza to intercept an [Islamic Jihad] activist," Gideon Ezra, the public security minister, told Israel’s Army Radio. "It was unsuccessful. An opportunity presented itself. Any means to neutralise the organisation are relevant and possible."

Military officials said that the Islamic Jihad attacks that left an Israeli settler dead in the West Bank and killed a soldier in Gaza were prompted the shift in strategy, even though the movement has not publicly abandoned the ceasefire.

Eleven more Islamic Jihad suspects were arrested today, to add to the 52 held in raids a day earlier, in further signs that Israel is focusing it attention on that group in what it sees as Mr Abbas’s failure to confront the militants.

Islamic Jihad resumed mortar bomb and rocket salvoes against Jewish settlements in Gaza in retaliation for the Israeli sweeps to capture wanted militants.

Khaled al-Batsh, a senior Islamic Jihad leader in Gaza, gave warning of "terrible consequences" if Israel carried through its assassination threat and said the relative quiet would end. "This decision is meant to escalate violence against our people. The calm would thereby end. We will not be dictated to by Israel," he said.

The violence in Nablus was yet another signal that the truce could unravel and bring chaos to the already fraught Israeli plan to pullout out of settlements in Gaza and the West Bank within two months.

Gunmen fired in the air and waved their weapons angrily, startling Mr Qureia who had been in the sports club haranguing an audience of militants saying that the Palestinian people were desperate for quiet and order.

As the shots rang out Mr Quriea’s bodyguards stood at window and trained their weapons on the gunmen in the streets below before he and other ministers in his entourage left.

Mahmoud al-Khatib, who claimed to have fired at the building, said his frustration had boiled over because of Palestinian officials’ treatment of his father, jailed by Israel for 21 years.

"Officials live in luxury and we, the ones who gave so much to Palestine, have got nothing," said Mr al-Khatib. "I reached a point where I’m willing to kill so I can take back my rights, my father’s rights, and the rights of all those like us."

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