Prime Minister Najib Mikati said on TV that Lebanese army reinforcements went to two neighborhoods to "put an end to what happened."
The clashes were between Lebanese Alawites who support the Syrian government and Sunni Muslims who oppose it. There also had been a large demonstration in Tripoli in support of the Syrian people.
The clashes in Tripoli killed one soldier and three civilians and injured two soldiers and 10 civilians, the army said. Lebanon's National News Agency said one of those killed was an official with the Democratic Arab Party, an Alawite entity.
"I asked the military and the security forces to impose the law and order in the city and strike with an iron fist," said Mikati, who noted that authorities are investigating.
"I am not accusing anyone. We don't know who started the clashes," he said. "The timing is suspicious, and the civil peace is a red line that no one can cross." (read more)