Six people, including a 15-year-old schoolboy, were killed and 22 others wounded on Saturday in sectarian clashes in the northern Lebanese city of Tripoli, a security source told AFP.
The Lebanese army, which deployed in the city and evacuated children from the school where the teenager was killed, said seven soldiers were among those hurt in the ongoing clashes.
Violence regularly erupts between Alawite residents of the Jabal Mohsen neighbourhood, who support their co-religionist Syrian President Bashar al-Assad, and Sunnis from the Bab al-Tebbaneh district, who back Sunni-led Syrian rebels.
Two of the fatalities were named as 15-year-old Omar al-Haswani, who was killed inside the Luqman school, and a man in his thirties called Jihad Merab. They were both Sunnis from Bab al-Tebbaneh.
The security source said two other residents of the Sunni neighbourhood had also been killed, along with a Palestinian and a Syrian, but there were no immediate details on their names or ages.
The source said at least 22 people were wounded in the fighting, including seven soldiers.
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The army said in a statement that troops were on the ground responding to sources of fire, adding that a civilian from Jabal Mohsen had been injured earlier in the day by gunfire in a different Sunni neighbourhood.
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.
In response, residents of neighbouring Bab el-Tebbaneh raised the flag favoured by rebels seeking the ouster of Assad.
The same day, gunmen shot and wounded four Alawite workers in the city, prompting condemnation and demonstrations by Alawite residents.
Tripoli's population is 80 percent Sunni and 11 percent Alawite -- an offshoot of Shiite Islam -- and violence between the two communities dates back to Lebanon's 1975-1990 civil war.
But the tensions have been aggravated by the conflict in Syria, and the city was struck by a deadly double car bombing in August that killed 45 people.