An Israeli soldier was also killed and four wounded in the operation in the city of Nablus, which ended when soldiers blew up an apartment building where Mohammad al-Hanbali had been holed up, making 28 families homeless.

The spectacle of the seven-storey structure crumpling in a heap of dust was likely to give ammunition to opponents of Abbas's efforts to promote a US-backed peace plan and persuade President Yasser Arafat to hand over control of Palestinian security forces.

The army said naval commandos, who also participate in ground-launched attacks, raided the building to detain Hanbali, 27, who opened fire at them from an elevator shaft where he had been hiding.

Israeli security sources said he was chief commander of Hamas militants in the northern West Bank and responsible for the deaths of dozens of Israelis in suicide bombings in a three-year-old Palestinian uprising for statehood.

The raid was launched a day after Abbas, a proponent of the faltering peace "road map," called on Palestinian legislators to back him or sack him.

The outcome of the Abbas-Arafat face-off could determine the fate of the peace plan that has been nearly erased by a surge of violence since the collapse last month of a truce militants declared in June.

In an apparent bid to defuse the crisis, the Palestinian parliament was due to follow an inconclusive meeting on Thursday with a closed-door session on Saturday to hear more from Abbas on his dispute with Arafat.

Israel has stepped up sweeps for militants in West Bank cities since the disintegration of the cease-fire underpinning the road map.

Accusing Abbas of failing to carry out a crackdown on militants mandated by the plan, Israel has also killed 11 Hamas men and four bystanders in helicopter missile strikes in the Gaza Strip, attacks Palestinians described as assassinations.

Abbas, 68, appointed by Arafat in April under international pressure but lacking his rival's grassroots popularity, pledged his commitment to the road map on Thursday but stopped short of asking for a vote of confidence to strengthen him.

Palestinian officials have accused Israel of sabotaging peace moves through army raids and by failing to pull troops back from West Bank cities under the terms of the road map.

The plan calls for an end to three years of violence and the start of mutual confidence-building steps leading to the creation of a Palestinian state by 2005.