JERUSALEM (AP) - Critics from all sides decried Israeli Prime Minister Ariel Sharon yesterday for his handling of the siege of Yasser Arafat's headquarters, after U.S. pressure forced him to pull back Israeli troops and end the 10-day standoff.

Meanwhile, violence flared in the West Bank city of Nablus, where Israeli troops killed two Palestinian boys, ages 10 and 11, Palestinian officials said. Israeli soldiers enforcing a curfew in the city and a neighboring refugee camp clashed first with stone-throwing youths, then with Palestinian gunmen, witnesses said.

Sharon was in Moscow yesterday as the criticism swirled over the decision the day before to pull troops out of Palestinian leader Arafat's compound in the West Bank town of Ramallah. Some said Sharon and his government had underestimated Washington's determination to keep the Israeli-Palestinian conflict from undermining the campaign against Iraqi leader Saddam Hussein.

"Sharon is leaving behind a colossal failure, the most notable failure since the beginning of his term in office," commentator Hemi Shalev wrote in the newspaper Maariv.

A new threat to his coalition emerged at a convention of his senior partner, the moderate Labor Party, over a domestic issue - the state budget. Sharon has said that if the budget is not passed by the end of October, he will call an election.

Labor members of the Cabinet had already decided to support the budget - and thus stay in the government - partly because the possibility of a U.S. war with Iraq makes it an awkward time to display political divisions. However, party delegates yesterday voted to force their ministers to convene another convention to report on the budget negotiations before the vote in parliament, challenging the authority of the party leader, Binyamin Ben-Eliezer.

Outbursts of violence continued in Palestinian areas.

Gunfire broke out yesterday in downtown Nablus on the West Bank. Witnesses said Palestinian gunmen apparently fired on soldiers and the Israelis fired back. Black smoke rose from one building. Helicopters and military ambulances arrived at the scene.

Earlier, an 11-year-old Palestinian boy was killed in the Balata refugee camp near Nablus when soldiers enforcing a curfew fired from tanks at children who threw stones while on their way to school, doctors said. The military said soldiers had fired at a youth who was about to throw a firebomb.