Gaza City ? Gunmen stormed into a mourning tent for Yasser Arafat on Sunday night shortly after the arrival of the new leader of the Palestine Liberation Organization, firing weapons and setting off a chaotic clash with Palestinian police in which at least two officers were killed, according to witnesses and medical officials.

Bodyguards for Mahmoud Abbas, a former prime minister, shoved him to the ground, and hundreds of people dove for cover as the gunmen and security forces traded fire, according to witnesses and television footage.

As head of the PLO, Abbas is regarded as the most powerful Palestinian leader following Arafat’s death.

Abbas said later that the clash was not an assassination attempt. Speaking on Palestinian television, he said that “because of the crowdedness at the location there was anarchy and there was shooting in the air, and therefore we requested the people to leave.”

Yasser Abed Rabbo, a Palestinian government spokesman, said it was a “spontaneous” clash between armed groups, not a planned attack.

The incident — coming just three days after Arafat’s death and involving one of the four men who have assumed his responsibilities — underscored widespread Palestinian concerns about violence and lawlessness that could erupt if a power vacuum takes hold. Arafat, who was 75 at his death, groomed no successor.

The Palestinian Authority, which Arafat headed, announced Sunday that elections for its president would take place Jan. 9.

About five minutes after Abbas arrived at the mourning tent in Gaza City, approximately 20 armed men burst into the crowd where he and other senior Palestinian leaders, including former Gaza security chief Mohammed Dahlan, were greeting local officials and residents paying their respects to Arafat, who was buried Friday in the West Bank city of Ramallah.

“Abbas and Dahlan are agents for the Americans!” the gunmen shouted, according to footage taken by Associated Press Television News. Some of the gunmen yelled, “No to Abbas! No to Dahlan!”

Mahmoud Abbas, former Palestinian prime minister and the successor of Yasser Arafat as PLO chief, is hustled away by bodyguards after gunfire erupted at a tent set up for mourners of Arafat in Gaza City. Two security guards were killed Sunday and five people were wounded, hospital officials said.

The gunmen began firing into the air and uniformed Palestinian security guards returned fire as Abbas’s bodyguards pushed him to the ground. Screams filled the air, with hundreds of people seeking cover and overturning white plastic chairs.

Witnesses said the gunmen were from the al-Aqsa Martyrs Brigades, the armed wing of the mainstream Fatah political movement, of which Abbas is now second in command, the Arab satellite network al-Jazeera and other news outlets reported.

The al-Aqsa Martyrs Brigades, one of the main militant groups that has sponsored suicide bombings against Israelis, is highly decentralized, and its militant cells often act on their own. It was unclear whether the incident signaled a significant backlash by the group against Abbas, a moderate. Al-Aqsa is generally sympathetic to the younger generation of Palestinian leaders.

Early reports said the Fatah Central Committee had chosen Abbas as its candidate in the Jan. 9 election, but Abbas Zaki, a member of the committee, denied the claim, according to the Agence France-Presse news service. Such a move would pre-empt the candidacy of anyone else, particularly Marwan Barghouti, the former head of Fatah in the West Bank and a reputed founder of the al-Aqsa Martyrs Brigades who is serving a life sentence in an Israeli prison.

It could not be determined whether the gunmen were angry at the reports that Fatah had selected Abbas over Barghouti. Such an announcement could signal a much-anticipated battle between Fatah’s old guard and young reformers who have done most of the fighting in the current Palestinian uprising.