Israeli warplanes have struck a Palestinian guerrilla target just south of the Lebanese capital Beirut.
Army officials said a "terrorist base" was targeted in response to a strike on an Israeli naval vessel by militants in Lebanon earlier in the day.
Local officials said Israeli jets fired several rockets at the Naameh hills, about 20kms (12 miles) south of Beirut.
The Syrian-backed Popular Front for the Liberation of Palestine-General Command has a base in the area.
A spokesman for the group said the planes, "attacked humanitarian positions and a clinic".
"So far there are no human losses, only material losses," the spokesman was quoted by the Associated Press as saying.
There was no word on casualties.
The Israeli military has given few details about the raid saying only that it had targeted a base "used as a platform for terrorist activity in Lebanon".
"The state of Israel is determined to stop terror acts emanating from Lebanon and places responsibilities for these terror activities on the governments of Lebanon and Syria," the army said in a statement.
Israel has in the past carried out air strikes against Hezbollah targets in Lebanon.
There is constant tension between the two sides along the Israeli-Lebanese border.
Correspondents say it is rare for Israel to strike so deep inside Lebanon.