OCCUPIED JERUSALEM, 9 May — Israeli Prime Minister Ariel Sharon flew back home last night, cutting short a visit to the United States and vowing revenge after a Palestinian bomber killed 15 people south of Tel Aviv on Tuesday evening. "He who rises up to kill us, we will pre-empt it and kill him first," Sharon said earlier before leaving Washington.

As calls mounted in Israel for tough action, ranging from a new military offensive in the West Bank to exile for Palestinian President Yasser Arafat, the Palestinian Authority announced the arrest of 14 people in Gaza for alleged involvement in the Tel Aviv bombing. And Arafat ordered Palestinian security forces to foil any attempt to attack Israeli civilians.

Palestinians in the Gaza Strip braced for the possibility of an armed assault after Israeli media reported that the bomber came from Gaza.

Sharon faced criticism from right-wing politicians that he wound down the last offensive too soon without finishing Israel’s declared task of eliminating Palestinian fighters.

He also came under fresh attack for the ferocity of the offensive. The United Nations condemned it in a vote on Tuesday.

The vote in the UN General Assembly on an Arab-initiated resolution, which had been rejected by the more powerful Security Council, was 74 to 4. But 54 countries were jolted into abstaining after the bombing while the assembly was in session. They included virtually every eastern and western European nation, Japan, Australia, New Zealand, Canada and several Latin American countries. Russia voted in favor.

Secretary-General Kofi Annan yesterday sought cooperation from Israel, which has already rejected one UN fact-finding mission, to provide him with details for a report the General Assembly ordered on Israeli military action in the West Bank.

The assembly late on Tuesday asked Annan to prepare a report on what happened in the Jenin refugee camp and elsewhere in the West Bank, based on "available resources and information."

UN spokesman Fred Eckhard noted that the assembly called for a report that was broader in scope than Jenin, where a mission approved by the Security Council was supposed to go. Israel at first objected to the composition of the team but when the team was expanded it raised objections to the mandate. Annan then canceled the mission.

Fowzi Shubokshi, the Kingdom’s permanent representative at the United Nations, said Israel’s refusal to receive the UN fact-finding mission confirmed the reports that its forces had committed massacre of Palestinians at the camp. He said the UN decision to disband the mission was a "dangerous setback for the international body." Shubokshi wondered why the United Nations, which has used its military power in the past to implement its resolutions, was stood helpless before Israeli arrogance and intransigence.

In Washington, Secretary of State Colin Powell said the United States believed that reform of the Palestinian Authority was "essential" — but not necessarily a prerequisite — for the resumption of political talks between Israel and the Palestinians.

Powell’s comments appeared to place the US position at odds with that of Sharon, who is insisting that the Palestinian Authority be totally revamped before such talks.

Powell said reform of the authority had been a major topic of conversation between US President George W. Bush and Sharon at the White House, but said conditioning negotiations on it had not been raised.