Palestinian sources reported on Thursday that two people were killed, when unidentified gunmen opened fire in Lebanon's largest Palestinian refugee camp.
The latest attack will be a threat to the ceasefire which ended several days of clashes between Fatah and a militant group in the camp.
A source from the Fatah Palestinian group said a Fatah official and a civilian had been killed by "unidentified gunmen" overnight in Ain al Hilweh in southern Lebanon.
Palestinian officials also said the ceasefire remained in place despite the attack and that high-level contacts were made during the night to ensure it would be respected.
The refugee camp formerly known as Ain al Hilweh is an impoverished, overcrowded camp near the coastal city of Sidon, home to some 61,000 Palestinians, including 6,000 who fled the war in Syria.
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.
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.