US did not have advance warning of Israeli strike in Beirut: Pentagon

US Defense Secretary Lloyd Austin said he did not have any advanced warning of Israel's strikes in Beirut that targeted Hezbollah's central headquarters but spoke to his Israeli counterpart as the operation was already underway.

Austin declined to offer any assessment of the strike, amid speculation about the fate of the Lebanese fighter group's head Sayyed Hassan Nasrallah. Austin said he would be speaking with Israel's Defense Minister Yoav Gallant again "soon" for an update.

"We had no advance warning. My call with Minister Gallant took place while the operation was actually already underway," Austin told reporters as he landed at Joint Base Andrews outside Washington after a trip to London.

"As you know, this operation took place just a couple of hours ago, and they're still making assessments. I don't have any further information or specifics to provide you at this time."

The strike could have far-reaching implications for the Middle East as Israel shifts its attention from its nearly year-old war with Iran-aligned Hamas in Gaza to operations against Hezbollah.

Iran's embassy in Lebanon said on X that the strike represented a dangerous game-changing escalation that would "bring its perpetrator an appropriate punishment."

Jordan's foreign minister said Israeli Prime Minister Benjamin Netanyahu was driving the region to a full-fledged war.

Austin has been publicly warning that a full-blown war between Hezbollah and Israel would be devastating for both sides and on Friday renewed calls for diplomacy.

"An all out war should be avoided," Austin said.

"Diplomacy continues to be the best way forward, and it's the fastest way to let displaced Israeli and Lebanese citizens return to their homes on both sides of the border."

Pentagon spokesperson Sabrina Singh, speaking to reporters earlier on Friday at the Pentagon, declined to say what Gallant told Austin about the operation and whether it specifically targeted Nasrallah. The Pentagon declined to speculate on whether Nasrallah was still alive.

Asked what Austin may have communicated to Gallant given the Israeli strike's potential impact on US efforts to secure a ceasefire between Israel and Hezbollah, Singh declined to offer specifics, but she said the defence secretary is always frank in his conversations with his Israeli counterpart.

"Look at just the engagements that the secretary and Minister Gallant have had over the last two weeks, speaking regularly. I think if there was any type of fracture in trust, you wouldn't see those type of levels of calls and engagements occurring frequently," Singh said when asked if the lack of advance notification by Israel indicated a lack of trust.

The Israeli military said it had targeted Hezbollah's central headquarters in Beirut's southern suburbs on Friday in an attack that shook the Lebanese capital and sent thick clouds of smoke over the city.

Senior Hezbollah commanders were the target of Israel's strike on the group's central headquarters in Beirut's suburbs on Friday but it was too early to say whether the attack took out Nasrallah, a senior Israeli official said on Friday.

"I think it's too early to say, but, you know, it's a question of time. Sometimes they hide the fact when we succeed," the official said.