People gather near a damaged building at the scene of an Israeli missile strike in the southern suburbs of Beirut on Friday. AP

Kirby, speaking to reporters, said he could not comment on the latest strikes but reiterated that the Biden administration is seeking to avoid an escalation in the region.

UN peacekeepers in Lebanon urged immediate de-escalation as hostilities rumbled on at the Lebanese-Israeli border on Friday, following Israel's most intense airstrikes in nearly a year of conflict with Hizbollah.

Israel's military said on Thursday it had struck hundreds of Hizbollah rocket launchers that had been set to fire towards Israel, in what security sources in Lebanon said was the heaviest such attack since hostilities began last October.

The UNIFIL peacekeeping force in south Lebanon said on Friday morning that the previous 12 hours had seen "a heavy intensification of the hostilities" across the Lebanese-Israeli border and in its area of operations.

"We are concerned at the increased escalation across the Blue Line and urge all actors to immediately de-escalate", UNIFIL spokesperson Andrea Tenenti told Reuters, referring to the line that delineates the border between Lebanon and Israel.

Israeli airstrikes on Friday hit at least three villages in south Lebanon, according to security sources in Lebanon and Hezbollah's Al Manar television, which broadcast footage of a cloud of smoke rising from one of the attacks.

Earlier, Britain's foreign minister David Lammy chaired a meeting of the government's emergency committee, known as COBR, on Friday to discuss the latest situation in Lebanon.

"The Foreign Secretary has chaired a meeting of COBR this morning on the latest situation in Lebanon and to discuss ongoing preparedness work, with the risk of escalation remaining high," the Foreign Office said in a statement.

Reuters