Gunmen killed an adviser to Palestinian leader Yasser Arafat in a street ambush early Tuesday, feeding fears of growing lawlessness ahead of a possible Israeli withdrawal from the Gaza Strip.

Arafat denounced the killing of Khalil al-Zaben (search), 59, as a "dirty assassination" and convened his Cabinet and national security council Tuesday to discuss what was seen as one of the most serious challenges yet to the Palestinian Authority (search).

The Palestinian Authority has been weakened by more than three years of Israeli-Palestinian fighting, and armed gangs, included gunmen with ties to Arafat's Fatah movement, are increasingly controlling the streets.

Al-Zaben is the best-known Palestinian to be killed in recent internal fighting. He was hit by 12 bullets as he left his Gaza City office. There was no claim of responsibility and security officials said publicly they had no suspects.

However, one official speaking privately said he suspected the assailants had ties to Fatah. Al-Zaben had made enemies in Gaza by filing detailed reports to Arafat about activities of various factions, the official said.

Last week, al-Zaben distributed a leaflet in Gaza in which he denounced "gangs of professional killers and assassins" whom he held responsible for a recent shooting attack that wounded a Fatah politician. Al-Zaben was a local publisher and also headed a human rights group funded by the Palestinian Authority.

Al-Zaben was given an official funeral Tuesday, attended by Palestinian Authority officials and scores of police officers. Tayeb Abdel Rahim (search), a senior Arafat aide, said in a eulogy that "the hand which dared to shoot you will be cut off."

The Palestinian Cabinet and national security council were discussing the killing at a meeting Tuesday, said minister Saeb Erekat (search).

"This chaos will not be tolerated. I believe the Palestinian government and security forces must take all action to end this chaos," Erekat said. "It is really undermining the Palestinian struggle to establish an independent state."

Israel's army chief, Lt. Gen. Moshe Yaalon, told a committee of the Israeli parliament Tuesday that Palestinian society "is rife with internal power struggles — maybe we can even call it 'anarchy' — revenge killings, local battles."

Yaalon told the closed-door meeting of the Defense and Foreign Affairs Committee that it was too early to say whether the turmoil could bring about a Palestinian leadership change, according to the Maariv daily's web site.

The shooting was the latest in a string of violent confrontations in Gaza and the West Bank.

On Saturday, about 15 masked, armed Palestinians barged into the Gaza City offices of the Palestinian Broadcasting Corporation (search), demanding jobs at gunpoint.

In a similar incident last Wednesday, about 20 masked men armed with submachine guns and hand grenades raided the Gaza City office of the Palestinian Land Authority (search), demanding land deeds be transferred to their names, employees said.

On Friday, the mayor of the West Bank's largest city, Nablus, resigned amid growing chaos and infighting between armed militias. Mayor Ghassan Shakaa (search) accused Arafat of not doing enough to prevent Nablus from plummeting into lawlessness. In November, Palestinian gunmen shot and killed Shakaa's brother.

At Gaza police headquarters recently, rival groups opened fire on each other after an armed man slapped the police chief. A policeman was killed in the exchange that followed, which involved Arafat's forces and men loyal to Gaza strongman Mohammed Dahlan (search), an Arafat rival. Later, Arafat and Dahlan met in an attempt to stop the violence.

There is concern that chaos will follow a planned Israeli pullout from most of the Gaza Strip. Islamic militant opposition groups could try to seize power.

In more than three years of fighting, Israel has attacked and destroyed the headquarters and infrastructure of many branches of the official Palestinian security forces. In most places, the uniformed forces barely function. In some cases, the security forces are active in militant activities.

Al-Zaben joined forces with Arafat in the 1960s and held a number of positions, including media adviser and personal secretary. He returned to Gaza along with Arafat and other exiled Palestinian leaders in 1994, under terms of Israeli-Palestinian interim peace accords. More recently, he published a weekly magazine devoted to Palestinian affairs and human rights.

Two of his brothers are Palestinian ambassadors in South America, and his son works as an airline pilot there. He is also survived by his wife and three daughters.

The Gaza journalists' association condemned the killing and called for the Palestinian attorney general to resign for his "failure" to protect civilians. The group urged Arafat to bring the attackers to justice.

The Popular Front for the Liberation of Palestine (search), a militant group, also condemned the killing.

"We hold the Palestinian Authority responsible for the continuation of attacks against journalists and other sectors of the Palestinian civil society," the group said.

Meanwhile, Israeli forces killed an unarmed Palestinian man during an arrest operation in the West Bank village of Yatta, the army said. Troops had surrounded the house of a fugitive, she said, and a man fled the structure.

Troops called on the man in Arabic to stop and then fired in the air, the army said. When the man did not respond to the soldiers' calls, they shot and killed him, it said.

In Washington, an Israeli delegation headed by Dov Weisglass, the head of Sharon's office, met National Security Adviser Condoleezza Rice and Secretary of State Colin Powell to discuss the prime minister's plan to unilaterally withdraw from parts of the Gaza Strip.

According to a statement from Sharon's office, the sides will hold more meetings in the coming days in Israel and the United States in an effort to arrange a Bush-Sharon summit.