Israeli airstrikes targeted a Palestinian faction loyal to the Syrian government in eastern Lebanon before dawn on Monday, Lebanese state media and the group said.
The strikes came just hours after the head of Lebanese Shiite movement Hezbollah threatened Israel after two drones fell on its Beirut stronghold in what he described as a targeted "drone attack".
The National News Agency said "three hostile strikes" after midnight hit Lebanon's eastern mountains near Qusaya town "where the Popular Front for the Liberation of Palestine - General Command has military posts".
"They responded well a barrage of anti-aircraft fire," it said.
PFLP-GC spokesman Anwar Raja told the Al-Mayadeen television channel that it was an Israeli strike.
The PFLP-GC has close ties to Hezbollah and Syria's government.
It has positions in the eastern region of Bekaa, as well as in Al-Naaemeh just south of Beirut.
Qusaya is only about five kilometres (three miles) from the Syrian border.
In July 2015, a security official said a blast at a PFLP-GC base there wounded seven people, while the Palestinian group blamed it on an Israeli strike.
On Sunday, Hezbollah chief Hassan Nasrallah threatened Israel after what he described as a targeted "drone attack" in a stronghold of his group in the south of Beirut.
"The time when Israeli aircraft come and bombard parts of Lebanon is over," he said.
"I say to the Israeli army along the border, from tonight be ready and wait for us," he said. "What happened yesterday will not pass."
Hezbollah, considered a terrorist organisation by Israel and the United States, is a major political actor in Lebanon and also a key government backer in war-torn Syria.
The latest incident also came after Israel on Saturday launched strikes in neighbouring Syria to prevent what it said was an Iranian attack on the Jewish state.
The strikes came just hours after the head of Lebanese Shiite movement Hezbollah threatened Israel after two drones fell on its Beirut stronghold in what he described as a targeted 'drone attack'.