Osama bin Laden's top deputy urged Palestinians to turn against president Mahmud Abbas and his secular Fatah party, in an audio message posted on the Internet on Sunday.
The recording, whose authenticity could not be independently confirmed, congratulated Muslims on the start of the Eid al-Adha feast of sacrifice. In it Ayman al-Zawahiri also implicitly criticised the Palestinian ruling Islamic movement Hamas for taking part in the political process.
"The Palestine-selling secularist traitors cannot possibly be your brothers, so neither confer on them legitimacy... nor participate with them in their Sharia-rejecting assemblies, nor sign with them the documents which throw away Palestine," said the Al-Qaeda second-in-command.
"How is it possible for Mahmud Abbas to be a brother of ours?" Zawahiri questioned, accusing him of complicity with the Israelis and Americans.
On December 20 Zawahiri slammed Hamas for recognising Abbas and running in elections last January. Hamas scored a shock victory over Fatah and took power in March, but its government has since been boycotted by Israel and the West.
But Fatah spokesman Tawfiq Abu Khussa slammed Zawahiri's words as "unacceptable".
"A man like Zawahiri does not in any way represent the Palestinians. He's behaving like a CIA spy -- he does not have the right to say these things and no right to interfere in Palestinian affairs," he said in Gaza.
The Fatah-linked militant group Al-Aqsa Martyrs Brigades said "these declarations sow division and serve the purpose of the Zionist (Israeli) occupation and have nothing to do with the fight against the occupier."
"We call on Zawahiri not to interfere in Palestinian affairs," the group said in a statement.
In Sunday's audio message, which does not specifically mention Hamas, Zawahiri said that victory in Iraq and Afghanistan was "not achieved by parliamentary elections... Rather, it was achieved with blood, martyrdom-seeking..."
He went on to congratulate mujahedeen fighters in Kashmir, Chechnya, the Philippines, Somalia, Algeria and Yemen, as well as Muslims being held at the US detention faciliity at Guantanamo in Cuba and at other jails around the world.
Zawahiri also paid homage to "Muslim women who kept their veils and preserved their modesty in the face of the crusaders to denounce the decadence and vileness of their civilisation".
The Egypt-born Zawahiri is regarded as the ideological powerhouse behind Al-Qaeda, and carries a 25-million-dollar US bounty for information leading to his arrest or death.