Rival members of two Palestinian security services fought running street battles in Gaza on Monday, witnesses said, in a fresh blow to stability in the Gaza Strip ahead of Israel's planned pullout next year.

Witnesses said at least six PA policemen were injured, one seriously, in gunfights in Gaza City between officers of the Palestinian Authority's internal security service loyal to Mouhamed Dahlin and military intelligence agents loyal to the cousin of Chairman Yasser Arafat, Moussa Arafat.

The identities of the casualties were not immediately clear. Neither agency commented.

In a separate incident, Hamas and Islamic Jihad activists exchanged fire during a squabble over control of a mosque in the northern Gaza Strip town of Beit Lahiya, Israel Radio reported. There were no injuries in the incident.

The Palestinian security apparatus has been hobbled by corruption charges and factional feuds as well as Israeli attacks on its infrastructure, which the Jewish state says has spawned militants waging a four-year-old revolt against it.

Moussa Arafat's appointment as chief of military intelligence in July drew violent street protests from Gaza activists who demanded reform in the Palestinian old guard.

On October 12, Moussa Arafat survived a car bombing against his convoy that he blamed on Palestinian enemies. He had been at odds with some Palestinian militants. One group, the Popular Resistance Committees, accused him of trying to kill its leader.

The deteriorating situation has posed the greatest internal challenge to Yasser Arafat since he returned from exile, and has raised the spectre of total chaos in Gaza once Israeli troops and settlers withdraw next year under a plan by Prime Minister Ariel Sharon to "disengage" from conflict with the Palestinians.