File Photo - Lebanese army soldiers block the main entrance of Burj Shamali Palestinian refugee camp, in the southern port city of Tyre, Lebanon, Friday, Dec. 10, 2021. AP
The officials, speaking to The Associated Press on condition of anonymity in line with regulations, said the fighting broke out after an unknown gunman tried to assassinate Islamist militant Mahmoud Khalil, killing a companion of his instead.
Later, Islamist militants assassinated a Palestinian military general from the Fatah group and three escorts, another Palestinian official told the AP.
Factions used assault rifles and rocket-propelled grenade launchers in the overcrowded Ein el-Hilweh camp as ambulances zoomed through its narrow streets to take the wounded to the hospital. Several residents fled the crossfire.
Palestinian factions in the camp for years have cracked down on militant Islamist groups and fugitives seeking shelter in the camp's overcrowded neighborhoods. In 2017, Palestinian factions engaged in almost a week of fierce clashes with a militant organization affiliated with the extremist Islamic State group.
Lebanon's state-run National News Agency said two children were among those wounded.
The escalation began when a gunman, known as 'Somali' opened fire on an Islamic activist at Ain Al-Hilweh's vegetable market, causing a foot injury and starting the escalation in the night from Saturday to Sunday.
Lebanese National News Agency, NNA, reported a heavily armed deployment between the Safsaf and Barkasat areas on Sunday.
The clashes stopped for several hours in the morning, though state media said there was still sporadic sniper fire. But they began again after the killing of the Palestinian general and his escorts.
The Lebanese Army in a statement said a mortar shell landed in a military barracks outside the camp wounding one soldier, whose condition is stable.
Ein el-Hilweh is notorious for its lawlessness and violence is not uncommon. The U.N. says it is home to some 55,000 people.
It was established in 1948 to host Palestinians displaced by Israeli forces during the creation of Israel.