An Israeli strike in the southern Lebanese city of Sidon killed a Fatah official on Wednesday, a senior member of the Palestinian group and a security source said.
It marked the first such reported attack on Fatah, the movement led by Palestinian president Mahmud Abbas, in more than 10 months of cross-border clashes between Israel and Lebanon's Hezbollah movement.
"The Israeli strike in Sidon killed (Fatah) group official Khalil Makdah," said Fathi Abu al-Aradat, a senior member of the group that rivals Gaza's Palestinian Islamist rulers Hamas.
A Lebanese security source confirmed the report to AFP, saying the strike hit his car.
An AFP correspondent at the site of the attack said a car was struck near the Palestinian camps of Ain al-Helweh and Mieh Mieh, adding rescuers had pulled a body from the charred vehicle.
Lebanon's official National News Agency said Makdah was killed "in a drone strike on his car".
Mounir Makdah, who heads the Lebanese branch of Fatah's armed wing, the Al-Aqsa Martyrs' Brigades, told broadcaster Al-Mayadeen that his brother Khalil had been killed.
He told the channel his brother had been a commander in the Al-Aqsa Martyrs' Brigades.
Hezbollah and its allies have exchanged regular fire with Israel in support of its ally Hamas since the Palestinian militant group's October 7 attack on Israel sparked the Gaza war.
But Fatah has not announced any attacks on Israel from Lebanon since clashes began nor had it mourned members killed by Israeli fire in Lebanon.
Hamas and Fatah have been bitter rivals since Hamas fighters ejected Fatah from the Gaza Strip after deadly clashes that followed Hamas's resounding victory in a 2006 election.
Fatah controls the Palestinian Authority, which has partial administrative control in the Israeli-occupied West Bank.