GAZA, Sept. 7 - The president of the Palestinian Authority, Mahmoud Abbas, pledged Wednesday to track down the Palestinian gunmen who had assassinated his security adviser, a killing that delivered a new challenge to his leadership just days before Israeli troops are to leave the Gaza Strip.
Palestinian police officers guarded the site in Gaza where Moussa Arafat was shot to death early Wednesday. A Palestinian faction said it killed Mr. Arafat, a cousin of Yasir Arafat, because he was corrupt.
Yasir Arafat named Moussa Arafat as Gaza security chief in 2004.
Mr. Abbas also canceled a trip to New York next week for the opening of the United Nations General Assembly, which will now coincide with Israel's planned withdrawal of its soldiers from Gaza.
Mr. Abbas said he would punish those responsible for the fatal shooting of the adviser, Moussa Arafat, 61, a cousin of Yasir Arafat, the Palestinian leader who died last November. Mr. Abbas, who has been staying in Gaza during the Israeli pullout, convened his national security council and the security forces were placed on heightened alert.
In the attack early on Wednesday, about 100 gunmen stormed Moussa Arafat's four-story family compound in Gaza City after exchanging gunfire with his security guards for 30 minutes and dragged him in his pajamas to the street, where they shot him. Gunmen seized his 29-year-old son, Manhal, who also is a security officer, and wounded four bodyguards. The Palestinian authorities were trying to negotiate the son's release into the night.
The Popular Resistance Committees claimed responsibility and said that Mr. Arafat had been killed because he was corrupt and that more such killings could follow if the Palestinian Authority did not punish corrupt officials. The group is a faction founded by disaffected members of other militant groups after the Palestinian uprising began five years ago. It did not join other factions in agreeing to a temporary truce in February
Mr. Arafat "was famous for his corruption, and he committed many other crimes against the Palestinians," said a leader of the Popular Resistance Committees, who gave his name only as Abu Said. "The Palestinian Authority should have taken action against him. But they didn't do anything, and this is why we decided to assassinate him."
The Palestinian areas were mostly calm last month during the pullout of the settlers, and immediately afterward. But unrest has been renewed in recent days, raising questions about Mr. Abbas's ability to impose control after the Israeli departure. On Wednesday, Israel said that it intended to remove its soldiers from Gaza on Monday, three days earlier than previously announced, the Israeli media reported.
"This is a warning" to Mr. Abbas, said Raanan Gissin, a spokesman for Prime Minister Ariel Sharon of Israel. "He will be the one who will pay the price. This shows the lack of law enforcement, of control by the Palestinian Authority."
Ziad Abu Amr, a Palestinian lawmaker, said: "This is a test of the Palestinian leadership, and it comes at a time when they need to establish internal tranquillity. If the Palestinian Authority cannot establish control, then others will step into the vacuum."
The Arafat family compound is three blocks from the headquarters of the Palestinian Preventive Security forces. Residents throughout the area said the gunfire woke them, but no security officers came to the scene during the shootout, witnesses and Palestinian officials said.
Mr. Arafat had held a number of senior security posts since the formation of the Palestinian Authority in 1994. He had a reputation for ruthlessness and was widely suspected of corruption. Among his many rivals and enemies were the armed Palestinian factions and other security chiefs - including leaders of the Preventive Security forces.
He had been the subject of previous attacks, including rocket fire and a car bombing directed at him and his offices in the past two years. Both were believed to be the work of Palestinians.
In July 2004, when Yasir Arafat appointed him as Gaza's top security chief amid a wave of lawlessness, the announcement caused street protests. After the Palestinian leader died, his successor, Mr. Abbas, forced his longtime security chiefs to retire. Moussa Arafat was given a much less influential post of presidential security adviser.
The killing was part of a surge of unrest in Gaza in recent days.
Palestinian security force members have blocked roads in Gaza to demand higher pay. Unemployed Palestinians seeking jobs have clashed with the Palestinian security forces. A powerful explosion at the house of a family linked to the Islamic faction Hamas killed four people when explosives detonated accidentally.
And Tuesday, a large group of Palestinian youths tore through a fence and rushed toward Israeli troops in the Gush Katif settlement bloc in southern Gaza. The soldiers fired at the Palestinians as they climbed on a tank, killing one and wounding three.
