Troops deployed from 3 am (0000 GMT) on the streets of the impoverished neighbourhoods of Bab Al-Tebbaneh and Jabal Mohsen, both of which sustained severe damage in the overnight clashes, an AFP correspondent said.
The two districts have been the scene of repeated clashes between the rival pro- and anti-Syrian communities.
Prime Minister Najib Mikati, who has just formed a new government dominated by a pro-Syrian alliance and was in Tripoli, the city of his birth, when the fighting broke out, said civil peace was a "red line".
Among those killed in the clashes, which involved automatic weapon and rocket-propelled grenade fire, were a Lebanese soldier, an official from an Alawite party and a 14-year-old Sunni boy.
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The two districts have been the scene of repeated clashes between the rival pro- and anti-Syrian communities.
Prime Minister Najib Mikati, who has just formed a new government dominated by a pro-Syrian alliance and was in Tripoli, the city of his birth, when the fighting broke out, said civil peace was a "red line".
Among those killed in the clashes, which involved automatic weapon and rocket-propelled grenade fire, were a Lebanese soldier, an official from an Alawite party and a 14-year-old Sunni boy.
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