Fatah and Islamist groups have been fighting for four days in a Palestinian refugee camp in Lebanon, leaving 11 dead and more than 100 injured, Lebanese media reported on Monday.

The violence erupted on Thursday night in Ain al-Hilweh camp, where heavy weapons such as RPGs and machine guns were used. Hundreds of people fled their homes as a result. Some civilians in nearby towns were also hurt by bullets that flew out of the camp.

This is the second outbreak of clashes in the camp in a month. In March, 13 people died and thousands were displaced due to similar confrontations.

A Fatah militant’s killings triggered the clash in late July. Then, Fatah official Abu Ashraf al-Armoushi and four of his comrades were killed by militants in the camp. Fatah demanded that the killers of Armoushi be handed over.

Palestinian and Lebanese officials tried hard to stop the fighting, but none of their attempts worked as of Monday afternoon.