Islamic militants clashed with Fatah gunmen in a Palestinian refugee camp in southern Lebanon on Monday, killing at least two people, Palestinian security officials said.

It was not immediately clear what prompted the shootout in the Ein el-Hilweh camp, where gunfights are common between armed groups jockeying for power.

Monday's confrontation involved gunmen from the militant Asbat al-Ansar group, which is on a U.S. terrorism list and which Washington has accused of being linked to al-Qaida.

An official said one of the militants shot a Fatah member, igniting the clash with other gunmen from the mainstream Palestinian movement. His account could not immediately be confirmed.

Two bystanders died and a Fatah member was seriously wounded, said the officials, who spoke on condition of anonymity because they were not authorized to make official statements.

The echo of gunfire and rocket-propelled grenades reverberated in the camp and in the nearby city of Sidon. Some families in the teeming camp fled to safer areas.

Ein el-Hilweh is home to 70,000 people, making it the largest of Lebanon's 12 Palestinian refugee camps. It is notorious for gunbattles and tit-for-tat bombings between rival groups.

A number of fugitives live in the camp, which is under Palestinian jurisdiction and off limits to Lebanese authorities. Among the fugitives are members of Asbat al-Ansar, or Band of Partisans.