Lebanese authorities decided Monday to place Tripoli under army control for six months after a wave of sectarian killings linked to Syria's war left 11 dead in the main northern city.
The decision was taken at a meeting between President Michel Sleiman, army chief General Jean Kahwaji and Prime Minister Najib Mikati, the premier's office said.
"It has been decided, for a period of six months, to task the army with all necessary measures to restore security," his office said.
The army would also be in charge of carrying out arrests ordered by the judiciary.
Security measures such as patrols and checkpoints have already been increased in the port city, the military itself announced.
A man was killed Monday in Tripoli, a security source said, raising to 11 the toll in three days of sectarian clashes linked to the war in neighbouring Syria.
The man, Issa Tiba, was from the Alawite district of Jabal Mohsen, whose residents have been locked in fierce fighting with rivals in the neighbouring Sunni district of Bab el-Tebbaneh since Saturday.
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The clashes have wounded at least 61 people, among them 12 members of the Lebanese army, which responded to the sources of fire, the security source said.
Four people in the city died on Sunday, including two men shot by a sniper while they were driving a truck, an off-duty soldier and a women who died of wounds suffered a day earlier.
Lebanese newspapers published a picture of the two dead men on Monday, with the passenger shown slumped against the driver of the blood-stained vehicle.
All those killed, except Tiba, were from the Bab el-Tebbaneh neighbourhood.
Also on Sunday, an explosion caused a three-storey building in Jabal Mohsen to collapse, according to the security source and an official from the area.
The official accused Bab el-Tebbaneh residents of planting explosives in the building.
The ongoing clashes prompted most of the schools in the city to close, and businesses near the two neighbourhoods were also shuttered.
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.