“We are facing aggression… Our choice is to confront it until the last sacrifice, and we will not surrender,” Hezbollah leader Naim Qassem declared in his first speech since the latest round of fighting began.
Lebanese officials said at least 72 people have been killed, 437 injured and 83,000 displaced from their homes since Monday.
Iran has retaliated by striking US-linked interests as well as energy infrastructure in its Gulf neighbors.
Thirteen people have been killed in countries around the Gulf since the war began, seven of them civilians, including an 11-year-old girl from Kuwait.
Qatar said on Thursday it was evacuating residents living near the US embassy in Doha, after earlier announcing that it had foiled attacks at Hamad International Airport.
The United Arab Emirates, Saudi Arabia and Qatar all said they had intercepted Iranian missiles on Wednesday, including a drone that struck the kingdom’s giant Ras Tanura refinery.