Israeli cabinet minister Ophir Pines praised Abbas for "an unprecedented step" in dismissing the three, members of Yasser Arafat's old guard, in response to violence that flared after Tuesday's summit in Egypt with Prime Minister Ariel Sharon.

The United States, which has pledged renewed commitment to Middle East peacemaking after Abbas succeeded Arafat last month, also praised the dismissals.

The United States said Thursday it still gave its firm backing to Palestinian president Mahmud Abbas, after Islamic radicals fired on Jewish settlements in Gaza despite a ceasefire.

"President Abbas has made clear his commitment to end violence and terror," State Department spokesman Adam Ereli told reporters in Washington. "This is a sign of his commitment and his determination to follow through."

Palestinian officials said Abdel-Razek al-Majaydeh, public security chief for the West Bank and Gaza, Palestinian Authority police chief Saeb al-Ajez and Omar Ashour, commander of the security forces in the southern Gaza Strip, were all fired.

Six lower-ranking commanders also lost their jobs.

"Nobody can shirk their duties, and measures will be taken to boost the capability of the security services in accordance with decisions taken at the political level," Palestinian Security Council member Jibril Rajoub told Reuters.

In another reminder of armed chaos in the Palestinian street challenging Abbas, dozens of gunmen including Hamas militants stormed into a Gaza City prison on Thursday and shot dead three inmates in a settling of scores between feuding clans.

Some 50 mortar bombs and rockets hit settlements in Gaza, but there were no casualties in the attacks by militants who have refused to participate in the ceasefire Abbas and Sharon announced at their groundbreaking meeting.

Israel signaled it would make no immediate military response. "If the Palestinians do not know how (to stop such attacks), we do," Israeli Defense Minister Shaul Mofaz said.

But, referring to Abbas's intention to end more than four years of violence, Mofaz added: "We cannot let this historic opportunity slip through our fingers."