Lebanese security officials say a masked gunman fatally shot a Fatah member in a Palestinian refugee camp in southern Lebanon, the Associated Press reported.
The officials say the 26-year-old fighter, Mustafa Khatib, was killed instantly.
He was shot by unknown assailant who then fled into the maze of alleys of Ein el-Hilweh camp near the southern city of Sidon.
The officials spoke on condition of anonymity because they were not authorized to speak to the media.
Thursday's killing is believed linked to a power struggle between Palestinian President Mahmoud Abbas' Fatah group and Islamic militants based in the camp, the largest of Lebanon's 12 Palestinian camps.
Fatah members and militants from al-Qaida followers of Jund al-Sham have recently clashed there.