The Israeli military said it carried out a “targeted strike” in the Lebanese capital on Friday, while two security sources told Reuters the southern suburbs of Beirut had been hit.

Hezbollah’s al-Manar TV reported “an attack” on the area.

“The IDF (Israel Defense Forces) conducted a targeted strike in Beirut. At this moment, there are no changes in the Home Front Command defensive guidelines,” the Israeli military said, providing no further details.

A thick cloud of smoke could be seen rising over the capital, according to a Reuters live feed, after residents said they heard a loud blast.

Hezbollah pounded northern Israel with 140 rockets Friday, a day after the militant group’s leader Hassan Nasrallah vowed to retaliate against Israel for a mass bombing attack, the Israeli military and the militant group said.

Israel’s military said the rockets came in three waves Friday afternoon targeting sites along the ravaged border with Lebanon.

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Hezbollah said it had targeted several sites along the border with Katyusha rockets, including multiple air defence bases as well as the headquarters of an Israeli armored brigade they said they’d struck for the first time.

Hezbollah said the rockets were in retaliation for Israeli strikes on villages and homes in southern Lebanon.

Click to play video: 'Second wave of attacks targeting Hezbollah'

Hezbollah and Israel have exchanged near-daily fire since Oct. 8, a day after the Israel-Hamas conflict’s opening salvo, but Friday rocket barrages were heavier than normal.

Nasrallah on Thursday vowed to keep up daily strikes on Israel despite this week’s deadly sabotage of its members’ communication devices, which he described as a “severe blow.”

Two days of attacks widely blamed on Israel targeted thousands of Hezbollah pagers and walkie-talkies, and have heightened fears that nearly a year of near-daily exchanges of fire between Hezbollah and Israel will escalate into all-out war.

Israel has neither confirmed nor denied involvement in the attacks.

–with files from Associated Press