Masked gunmen executed two Palestinians accused of collaborating with Israel today, including one who was machine gunned in a town square in the West Bank.
Underlining growing lawlessness in Palestinian areas, militants of al-Aqsa Martyrs Brigades snatched Mr Fadel Odeh (22) drove him to the centre of Tulkarm, forced him out of the car and killed him, witnesses said.
A crowd gathered and youths stepped on the man's body.
A second man Mr Amjad Ajaj (25) was found shot dead north of the West Bank town, residents said.
Palestinians have killed scores of their brethren accused of helping Israeli forces seek out and kill militants during fighting that erupted in September 2000.
International human rights groups have condemned the vigilante killings.
The latest killings have added to a climate of anarchy that has gripped the West Bank and Gaza Strip in recent months, posing the stiffest internal challenge yet to Palestinian President Yasser Arafat's rule.
Al-Aqsa, an armed group in Arafat's Fatah movement, said the men killed on Monday had helped Israeli forces hunt down militants in a neighbouring village where the two lived. "They were responsible for the martyrdom of a number of Hamas, Fatah and Islamic Jihad activists," it said in a statement.
Mr Izz al-Din al-Sharif, Tulkarm district governor, said Israel, which has crippled Palestinian security services during a four-year uprising, was responsible for the chaos.
"We have neither arms nor prisons to impose rule of law," he said. "Any militant group can take people and claim that they are collaborators and kill them. This has to come to an end."
Israel has accused Palestinian security forces of turning a blind eye to militant violence, and some security men have aided or carried out such attacks.
Israeli soldiers shot dead an unarmed Palestinian in the Gaza Strip overnight.
An Israeli source said troops fired at a Palestinian spotted crawling toward an army outpost on a road leading to a Jewish settlement bloc in central Gaza late last night.
Soldiers later found that the man had no weapon, the source said.
Soldiers also shot and wounded two Palestinians near Gaza City today as the men tried to bypass a closed beach road outside the Netzarim settlement, Palestinian medics said.
The shootings occurred shortly after Israel killed a senior Hamas commander in an air strike yesterday, accusing him of having played a key role in making crude Qassam rockets.
Hamas has vowed revenge.