Three members of the Islamist group Hamas were killed and others injured in a shooting on Sunday in the Palestinian camp of Burj al-Shemali in Lebanon, the group said, blaming the bloodshed on rival forces loyal to the Palestinian Authority.

Two Hamas officials told Reuters earlier four people had been killed. The statement issued by Hamas said members of the National Security Forces, who belong to the Palestinian Authority, carried out the attack.

Palestinian Authority officials condemned the attack, rejected Hamas' allegation and urged all sides to wait for the results of an investigation.

The Palestinian Authority and Hamas have been bitter rivals since the 2007 brief civil war in the Gaza Strip, which ended up in Hamas's control, while the Palestinian Authority continued to have limited control of the Israeli-occupied West Bank.

The shootings took place during the funeral of a Hamas supporter who was killed in an explosion on Friday night in the camp in the southern Lebanese port city of Tyre.