The Israeli air force struck a Palestinian group in Lebanon on Friday, officials said, hours after a different organisation said it fired four rockets at the Jewish state from Lebanon.
Israeli aircraft "targeted a terror site located between Beirut and Sidon in response to a barrage of four rockets launched at northern Israel yesterday [Thursday]," the military said.
"The pilots reported direct hits to the target."
Lebanon's NNA news agency said the target was a position of the Popular Front for the Liberation of Palestine - General Command (PFLP-GC), a hardline but secular militant group which said it had nothing to do with Thursday's rocket fire.
The salvo of four rockets, which caused damage but no casualties, was claimed by the Abdullah Azzam Brigades -- an Al-Qaeda-linked group which claimed similar rocket fire on Israel in 2009 and 2011.
Israeli army spokesman Brigadier General Yoav Mordechai said on Thursday that the rockets were "launched by the global jihad terror organisation" -- an apparent reference to Al-Qaeda.
Israeli Prime Minister Benjamin Netanyahu had threatened retaliation. "Anyone who harms us, or tries to harm us, should know -- we will strike them," he said on Thursday.
Two of the four rockets hit populated areas of northern Israel, causing damage but no casualties.
One struck in Gesher Haziv, a kibbutz east of the Mediterranean coastal town of Nahariya, AFP correspondents reported. Another hit Shavie Zion, a village between Nahariya and Acre, further south, Israeli media said.
A third rocket was intercepted by Israel's Iron Dome defence system, the army said. The fourth apparently struck outside Israel.
The airport in the main northern city of Haifa reopened on Friday for both domestic and international flights, after being closed by the military following the rocket fire, a spokesman for the Israeli Airports Authority told AFP.
Thursday's attack was the first of its kind since November 2011, when the same Palestinian jihadist group fired a volley of rockets from southern Lebanon at Israel. That fire too provoked retaliation by the Israeli military.
Defence sources said that the PFLP-GC base hit was in the Naameh valley. The Palestinian group has a number of heavily fortified positions in Lebanon.
Headed by Ahmed Jibril, the group is known for close ties with the Syrian regime of President Bashar al-Assad.
PFLP-GC spokesman Ramez Mustapha denied any link between his group and the rockets fired at Israel on Thursday.
Defence Minister Moshe Yaalon said Israel had "attacked terror targets in Lebanon ... in response to yesterday's launches at the Western Galilee."
"The State of Israel considers the Lebanese government responsible for what happens in its territory, and will not stand idly by while it is attacked or provoked and will not allow any element to disrupt the lives of our civilians," he said in a statement.
Lebanese President Michel Sleiman described the rocket fire as a violation of UN resolutions and of Lebanese sovereignty, and ordered security forces on Thursday to hunt down the perpetrators.