At least five people were killed, including a child, and 43 wounded in clashes between pro- and anti-Damascus regime supporters in north Lebanon on Tuesday, security and army officials said.
Two people were killed in Bab el-Tebbaneh, the mainly Sunni district of the northern port of Tripoli, and three died in the largely Alawite area of Jabal Mohsen in the city, a security official said, updating an earlier toll.
Ten soldiers were wounded as well as 33 civilians, both Sunni and Alawite, officials said, while a 13-year-old boy was among those killed.
"The clashes are continuing," an army spokesman said in the early evening, while the military said in a statement that soldiers were "chasing gunmen and have seized a quantity of guns, bombs and ammunition."
The fighting erupted late on Monday in Tripoli, home to a Sunni community hostile to the regime of Syrian President Bashar al-Assad, and a community of Alawites, an offshoot of Shiite Islam to which the Syrian leader belongs.
The clashes come days after a wave of kidnappings targeting Syrians in Lebanon, which lived under three decades of Syrian hegemony and remains deeply divided between supporters and opponents of Damascus.
Prime Minister Najib Mikati warned against the "absurd battle" rocking his hometown, Lebanon's second largest city.
"We have repeatedly warned against being drawn into this blaze that has spread around Lebanon," he said of the violence in Syria. "But it is clear that several parties wanted to push Lebanon into the conflict."
The violence was centred around the aptly named Syria Street, the symbolic "dividing line" between the rival Tripoli districts of Bab el-Tebbaneh and Jabal Mohsen.
Fires blazed in several buildings of the rival areas, where civilians evacuated their homes, an AFP correspondent said.
Tripoli has been rocked by deadly clashes in recent months between supporters and opponents of the Damascus regime as the conflict in Syria worsened with more than 23,000 reportedly killed there since March 2011.
The latest fighting erupted after a wave of tit-for-tat kidnappings of Lebanese citizens in Syria and Syrians in Lebanon.
In the latest episode last week, an armed Lebanese Shiite clan claimed it had kidnapped around 20 Syrians in retaliation for the abduction of a family member by a Syrian rebel group, which accused him of being a Hezbollah sniper.
Many more were reportedly seized as rioters went on the rampage in Beirut.
The opposition Syrian National Council accused authorities of failing to act over the attacks and implicitly blamed the Iran- and Syria-backed Shiite Hezbollah which heads a ruling coalition in Lebanon.
"Syrians in Lebanon have been abducted by political parties, and subject to arbitrary arrests by security agents, without the authorities so much as lifting a finger," the SNC said in a statement.
Hezbollah, considered Lebanon's most powerful military force, has denied any connection with the clan member or the kidnappings.
The SNC also said Lebanese army intelligence on Monday raided the home of a Syrian humanitarian activist and arrested two of his colleagues, and that they also arrested a Syrian lawyer.