At least three people have been killed due to heavy clashes between Al Qaeda-affiliated Jund al Sham group and members of Palestinian Fatah movement in the northern part of Ain al Hilweh camp, Lebanon's largest Palestinian refugee camp, near the southern port city of Sidon.
Sources reported the three killed in clashes which began on Monday were part of the Fatah movement. Several injured people were transported to hospitals in Sidon, according to Al Jazeera.
The sound of fierce gunfire and rocket fire could be heard from neighbouring Sidon as clashes raged.
In an attempt to protect the refugee camp, the Lebanese army reinforced its positions at the four main entrances to Ain al Hilweh, even though the army is not permitted to enter the camp under a tacit deal agreed upon following the events of the 1975-1990 civil war.
"Ambulances have not been able to enter the camp because of the intensity of the fighting, and because they're happening near the camp's entrances," one Palestinian source inside the camp told the AFP news agency, speaking on condition of anonymity.
Dozens of families fleeing the violent clashes were heading into Sidon, an AFP correspondent reported.
It is still unclear what sparked the clashes, each side placing the blame on the other.
The intensifying rivalry between Jund al Sham, who have been based in Ain al Hilweh camp since 2004, and Fatah movement has erupted into clashes several times during the past few months.
On Saturday, two people of the Fatah movement were killed when members of Jund al Sham tried to kill a high-level Fatah official.
The Ain al Hilweh camp, home to more than 100,000 Palestinian refugees, has gained notoriety as an impoverished camp used for refuge especially by fugitives, and as a mediator for settling of scores between different factions.
More than 450,000 Palestinians are registered in Lebanon with the United Nations Relief and Works Agency for Palestinian refugees, of whom mostly live under shabby conditions dispersed in the country's 12 official refugee camps.