Lebanese soldiers stormed a complex holding gunmen loyal to a radical Islamist cleric in the city of Sidon on Monday and arrested dozens of his supporters, security sources said, in a second day of clashes fuelled by neighbouring Syria's civil war.
The army said 12 soldiers had been killed in the southern Mediterranean port city, while security sources gave a higher army death toll of 18 and said 20 of Assir's supporters were killed. If confirmed that would make it one of the deadliest outbreaks in Lebanon since Syria's two-year conflict began.
The violence has strained fragile sectarian relations across Lebanon and residents fear that Syria-related clashes could drag their country back into civil war. Lebanon is still struggling to heal the wounds of 15 years of war between 1975 and 1990.
Hardline Sunni cleric Sheikh Ahmed al-Assir, who has accused the army of backing the interests of the Shia Muslim group Hezbollah, remains at large.
The army is trying to kill or capture him, after accusing him of killing soldiers "in cold blood" on Sunday.
Security forces were taking over houses around the mosque as they tried to control the area. A Reuters reporter saw clouds of smoke rising from the mosque and said Assir's office across the road was completely destroyed.
At least four tanks and several army vehicles were torched.
Sniper fire continued to hit nearby streets, so it was unclear how many buildings Assir's gunmen still controlled.
Sidon had been on edge since violence erupted last week between Sunni and Shia Muslim fighters, at odds over the Syrian conflict which pits mainly Sunni rebels against President Bashar al-Assad, who is a member of the country's minority Alawite sect, an offshoot of Shia Islam.
Tensions had been rising since the Lebanese Shia militant group Hezbollah sent fighters into Syria to lead the recapture of a strategic border town by Assad's forces.
The army said clashes broke out on Sunday after security forces detained one of Assir's followers. His supporters retaliated by opening fire on an army checkpoint.
Army commanders pledged to crush Assir's forces.
"We affirm to all Lebanese that the army is determined to eradicate strife, and will not halt its military operations until security is completely restored to the city," the army said in a statement on Monday.
At least 62 Assir supporters were arrested as soldiers combed the area they had seized, a security source said. One of the men captured had disguised himself in niqab, the head-to-foot cloak worn by religious Muslim women.
Lebanon's commissioner to the military court Judge Sakr Sakr said that Assir had been summoned "to be put on trial, along with 123 of his followers, including his brother and Fadil Shaker," a prominent Lebanese singer who abandoned his career to join Assir's ultraconservative group.
'Save your people'
"Come and save your people who are being massacred," said an appeal on Assir's Twitter account on Monday.
Assir, whose supporters accuse the army of giving cover to Hezbollah gunmen, called for people across the country to join him and demanded that "honourable" soldiers defect.
A statement by the military command on Sunday said the latest violence "has gone beyond all expectations. The army was attacked in cold blood in an attempt to light the fuse in Sidon, just as was done in 1975", it said.
Assir has a small group of staunch supporters, believed to be in the hundreds. But many Lebanese Sunnis see him as a militant and trouble maker.
Lebanon's Grand Mufti Mohammad Rashid Qabbani condemned the fighting, saying that there was never a justified reason to attack the armed forces.
But in the northern coastal city of Tripoli, a Sunni stronghold, masked Islamist gunmen roamed the streets on motorbikes and fired guns and sound grenades in a show of support for Assir.
Other supporters blocked main roads with cement blocks and burning tires.
Local media reported that some hardline Sunni mosques in Tripoli as well as the capital Beirut called for jihad, or holy war, in support of Assir.
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