The fighting in the northern port city of Tripoli also wounded 49 people, including 11 soldiers, the source told AFP.
Today four people were killed, two of whom were in a truck when they were shot dead by a sniper, while the third was the off-duty soldier and the last victim a woman who died of injuries sustained the previous day.
Their deaths came after a day of fierce clashes that lasted into the night, leaving six dead. .
The source said fires had broken out in buildings along the dividing line between the neighbourhoods as a result of the fierce clashes during which rocket-propelled grenades were also used.
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Tensions between the neighbouring areas date back to Lebanon's 1975-1990 civil war but have been exacerbated by the conflict across the border in Syria, where Alawite President Bashar al-Assad is battling a Sunni-led uprising.
The Lebanese army remained deployed in the coastal city in the north of the country today, responding to sporadic sniper fire.
At least eight soldiers were among those wounded in yesterday's clashes, and the dead included 15-year-old Omar al-Haswani, who was killed inside the Luqman school, near Bab el-Tebbaneh.
During the height of yesterday's violence, soldiers moved into the school to evacuate students in military vehicles.
The others killed included three residents of Bab el-Tebbaneh, as well as a Syrian and a Palestinian, the security source said.
Tensions have been running high in Tripoli since Thursday, when residents of Jabal Mohsen began flying Syrian flags to demonstrate their support for the Assad regime.
The same day, gunmen shot and wounded four Alawite workers in the city, prompting condemnation and demonstrations by Alawite residents.