Israel's military says it has struck targets linked to Palestinian militant group Hamas inside Lebanon and across the Gaza Strip.
The attacks come after a major rocket barrage on Israel from Lebanon, which the Israelis blamed on Hamas.
The Israel Defense Forces (IDF) said Hamas' "terrorist" infrastructure was hit in southern Lebanon.
Tensions are high after Israeli police raided Jerusalem's al-Aqsa mosque on consecutive nights earlier this week.
The mosque is Islam's third holiest site, and the Israeli raids have triggered violent confrontations with Palestinians inside and caused outrage in the wider region.
Israeli forces warn Hamas
Hamas chief Ismail Haniyeh, who was in Lebanon when the rockets were launched, said Palestinians would not "sit with their arms crossed" in the face of Israeli aggression.
In a statement early on Friday, the IDF tweeted that it had truck targets "including terrorist infrastructures belonging to Hamas in southern Lebanon".
The IDF added that it would not allow Hamas to operate from Lebanon and held Lebanon "responsible for every directed fire emanating from its territory".
