AIN EL-HILWEH, Lebanon, Dec 18 (Reuters) - Sporadic clashes broke out between armed factions in Lebanon's largest Palestinian refugee camp on Sunday after the bodyguard of an official there was killed, a witness and security officials said.

Fighters supporting the mainstream Fatah party clashed with gunmen suspected of belonging to extremist Islamist parties, shooting at each other and firing rocket propelled grenades in Ain el-Hilweh in southern Lebanon.

Armed clashes are common in the camp, which houses 50,000 refugees, and militant Islamists are known to operate there.

Hostility had been running high in the camp as regional tensions rise. Many in Lebanon worry unrest may spill over the borders as violence increases in neighbouring Syria, where the army is cracking down on an anti-government revolt.

One witness said masked men suspected of being from the Islamist group Jund al-Sham fired at a group of Fatah fighters and officials. He saw fighters carry away a wounded civilian and a Fatah official shot in the shoulder. (Reporting by Abdel-Halim al-Shihabi)