Tripoli, Lebanon --

Firing assault rifles and rocket-propelled grenades, Lebanese gunmen clashed in street battles Monday as sectarian tensions linked to the 14-month-old uprising in Syria bled across the border for a third day.

At least five people have been killed and 100 wounded in Lebanon's second-largest city since the gunbattles erupted late Saturday, security officials said. Residents say differences over Syria are at the root of the fighting, which pits neighbor against neighbor and raises fears of broader unrest that could draw in neighboring countries.

Lebanon and Syria share a complex web of political and sectarian ties and rivalries, which are easily enflamed. Tripoli has seen bouts of sectarian violence in the past, but the fighting has become more frequent as the conflict in Syria worsens.

The fighting camps break down along sectarian and political lines. On one side are Sunni Muslims who support the rebels trying to oust Syrian President Bashar Assad. On the other are members of the tiny Alawite sect, followers of an offshoot of Shiite Islam who are Assad's most loyal supporters.

The recent clashes were sparked by the arrest of Lebanese national Shadi Mawlawi, an outspoken critic of Assad. The Sunni fighters say the root of the latest conflict in Tripoli is across the border.

Groups of men, many carrying assault rifles and wearing military-style vests, ducked through trash-strewn alleys. The residents who remained in the neighborhood took cues from fighters about when to sprint across alleys to evade snipers. A car with children crouching in the back sped past one alley, a bullet pinging the pavement behind it.

The Lebanese army set up a small position a few hundred yards away from the fighting.

Mohammed Jaber, a 49-year-old fighter and Tripoli resident, said local fighting has been going on for decades in Tripoli. "The old has become new," he said. "Once the Syrian revolution started, we supported all efforts to get rid of the regime."