Israel launched air strikes before dawn on Friday in the Gaza Strip and Lebanon, reports AFP.
According to Israeli authorities, it was targeting Hamas in retaliation for several dozen rockets fired at Israel from both territories.
The strikes were launched around 4:30 am Israeli time (0130 GMT), hitting both the Gaza Strip and southern Lebanon, according to an Israeli army statement.
Explosions were heard by AFP in Lebanon's Tyre region as well as the Gaza Strip, where Israeli air raids had begun before midnight.
Tensions have soared between Israel and Palestinians during what is both the Jewish Passover and the Muslim holy month of Ramadan, prompting condemnations and calls for restraint from abroad.
The latest flare-up of violence comes after Israeli police clashed Wednesday with Palestinians inside Jerusalem's Al-Aqsa mosque -- Islam's third-holiest site.
On Thursday, Israel's army said more than 30 rockets had been fired from Lebanese territory into Israel in the largest escalation along the frontier since Israel and Hezbollah fought a 34-day war in 2006.
Army spokesman Lt. Colonel Richard Hecht had blamed Palestinian groups for the attack, saying they know "for sure it's Palestinian fire".
"Israel's response, tonight and in the future, will exact a heavy price," Prime Minister Benjamin Netanyahu said Friday just before the army announced the strikes in Lebanon.
He was speaking after a meeting with his security cabinet, which the presidential office said had "made a series of decisions, all of which were based on the recommendations of the (Israel Defence Forces)... in response to the firing at the citizens of Israel in both the north and the south".
"Israel's defence establishment is prepared to face any threat, on any front," said Defence Minister Yoav Gallant.
AFP journalists in Lebanon's Tyre region said they heard at least three explosions shortly after Friday's strikes, and a resident of a Palestinian refugee camp near there said he "heard explosions".
"At least two shells fell near the camp", Abu Ahmad told AFP.
Bd-pratidin English/Lutful Hoque
