Lebanon has sent troops to the port city of Tripoli after at least 10 people were killed in clashes linked to unrest across the border in Syria, BBC News reported.

Security forces were deployed after the country's Prime Minister Najib Mikati visited to try and stem the violence.

The clashes came after UN peace envoy Kofi Annan warned sectarian violence in Syria could spread across borders.

Recent weeks have seen increased clashes between armed Alawite groups and Sunni fighters in the city.

Armoured vehicles were seen on the streets of the city but no shots were fired, a Reuters report said.

Fighting was concentrated in Tripoli's Bab al-Tebbaneh district, a mostly Sunni Muslim community, and the pro-Damascus Alawite Jabal Mohsen neighbourhood.

Although there have been on-off clashes between gunmen in neighbouring Tripoli districts, Saturday June 2 death toll is believed to be the highest in a single day.

Community leaders in Lebanon have repeatedly warned of the possibility that the violence in Syria would spill over the border. Lebanon is already hosting thousands of Syrian refugees.

Last month, 11 Lebanese Shia Muslim pilgrims were abducted, reportedly by a Sunni rebel splinter group, in Syria.

On Friday, the leader of Lebanon's Hezbollah movement, Sheikh Hassan Nasrallah, called for their release.