The head of Hezbollah on Sunday threatened Israel after a "drone attack" on the Lebanese Shiite movement's Beirut stronghold, vowing to "do everything" to thwart future attacks.
Hezbollah, considered a terrorist organisation by Israel and the United States, is a major political actor in Lebanon and a key government backer in war-torn Syria.
The Shiite movement and Israel, which have fought several wars, have upped their belligerent rhetoric in recent months.
The pre-dawn incident in Beirut came just hours after Israel said it had launched strikes in neighbouring Syria to prevent an Iranian attack on the Jewish state.
Nasrallah said the strike had killed two Hezbollah members.
In a televised speech broadcast to thousands of supporters, Hezbollah chief Hassan Nasrallah said the attack on a target in Beirut's south was the first such "hostile action" since the 2006 war between Hezbollah and Israel.
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He said it violated a UN Security Council resolution ending the 33-day war, which killed 1,200 people in Lebanon, mostly civilians, and 160 in Israel.
Nasrallah said Hezbollah would do "everything" to prevent similar attacks.
"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." - 'Do not rest'
Addressing Israelis, he said: "Do not live, do not rest, do not be reassured, and do not bet for a single moment that Hezbollah will allow... aggression of this kind."