US President Joe Biden on Saturday called the killing of Hezbollah leader Hassan Nasrallah "a measure of justice for his many victims, including thousands of Americans, Israelis and Lebanese civilians."

In a statement a day after an Israeli air strike killed Nasrallah, Biden reiterated US support for "Israel's right to defend itself against Hezbollah, Hamas, the Houthis, and any other Iranian-supported terrorists groups."

Biden added that he had directed the defense secretary to "further enhance the defense posture of US military forces in the Middle East region to deter aggression and reduce the risk of a broader regional war."

Biden's statement came as the State Department ordered the family members of its diplomats in Beirut to leave, while authorizing the departure of some staff "due to the volatile and unpredictable security situation in Beirut."

The agency also urged US citizens to leave "while commercial options still remain available."

Military officials in Israel announced on Saturday morning that Nasrallah, who headed the armed movement for more than three decades, died in a bombardment targeting the group's headquarters in the southern suburbs of Beirut Friday night.

Hezbollah officially confirmed the death hours later.