Ongoing violence in Syria has spilled further into Lebanon, amid fears of a widening regional destabilisation.
At least seven people have been killed and more than 100 wounded in sectarian clashes in the city of Tripoli.
Lebanese army troops were forced to withdraw after coming under heavy fire when they tried to subdue heavy sectarian fighting.
The clashes between Sunni Muslims and Alawites, fuelled by tensions over the civil war in Syria, continued for a second night, security and medical sources said.
Gunmen in the Sunni district of Bab al-Tabbaneh and their Alawite rivals in Jebel Mohsen have exchanged gun and grenade fire, despite action by Lebanese troops deployed in the port city, residents said.
Two of the dead men were identified as residents of Jebel Mohsen, a hill inhabited mainly by Alawites which overlooks the predominantly Sunni area below, where five people were killed, medical sources said.
The area is one of Lebanon's most volatile sectarian fault lines and chronic Sunni-Alawite tensions in Tripoli have been heightened by the 17-month-old, mainly Sunni, uprising in Syria against President Bashar al Assad, an Alawite.
Meanwhile, the United States has expressed deep scepticism about suggestions by Syria's deputy prime minister that the regime was open to discussing President Assad's resignation.
"We saw the reports of the press conference that the deputy prime minister gave. Frankly, we didn't see anything terribly new there," State Department spokeswoman Victoria Nuland said.
Deputy prime minister Qadri Jamil said after talks in Moscow that Syria was ready to discuss anything in negotiations - even Mr Assad's departure.
"As far as his resignation goes - making the resignation itself a condition for holding dialogue means that you will never be able to reach this dialogue," he said.
But Mr Jamil added: "Any problems can be discussed during negotiations. We are even ready to discuss this issue."