BEIRUT (AP) -- Lebanon's third-largest city of Sidon was turned into a battle zone Monday as the military fought heavily armed followers of an extremist Sunni Muslim cleric holed up in a mosque.
Residents of the southern port fled machine-gun fire and grenade explosions that shook the coastal area in one of the deadliest rounds of violence, seen as a test of the weak government's ability to contain the furies unleashed by the civil war in neighboring Syria.
Official reports said at least 16 soldiers were killed and 50 were wounded in two days of clashes with armed followers of Ahmad al-Assir, a maverick Sunni sheik whose rapid rise is a sign of the deep frustration among many Lebanese who resent the ascendancy of Shiites to power, led by the militant group Hezbollah. More than 20 of al-Assir's supporters were killed, according to a security official who spoke on condition of anonymity because he wasn't authorized to talk to reporters.
The fierce battle that al-Assir's fighters were putting up showed how aggressive Sunni extremists have grown in Lebanon, building on anger not only at Syria's regime but also its allies in Hezbollah.
"Sidon is a war zone," said Nabil Azzam, a resident who returned briefly Monday to check on his home after having fled with his family a day earlier. "This is the result of all the sectarian rhetoric that has been building because of the war in Syria. It was bound to happen," he said by telephone, a conversation interrupted by a burst of gunfire.
Machine-gun fire and explosions from rocket-propelled grenade caused panic among residents, who also reported power and water outages. Snipers allied with al-Assir took over rooftops, terrorizing civilians, and many were asking to be evacuated from the heavily populated neighborhood around the Bilal bin Rabbah Mosque, where al-Assir preaches and where the fighting has been concentrated.
The military appealed to the gunmen to turn themselves in, vowing to continue its operations "until security is totally restored." By evening, the army had stormed the mosque complex, though not the mosque itself.
In addition to the more than 20 followers of the cleric who were killed, dozens of them were arrested, the security official said. There was no sign of al-Assir and it was unclear if he was in the mosque or had managed to escape.
The fighting in Sidon is the bloodiest involving the army since the military fought a three-month battle in 2007 against the al-Qaida-inspired Fatah Islam group inside the Palestinian refugee camp of Nahr el-Bared in northern Lebanon. The Lebanese army crushed the group, but the clashes killed more than 170 soldiers.
The scenes of soldiers aiming at gunmen holed up in residential buildings and armored personnel vehicles deployed in the streets evoked memories of Lebanon's 1975-90 civil war.
The challenges facing the Lebanese military resemble those that prevailed in that conflict, which eventually splintered the army along sectarian lines.
"It's the memory of this destructive war that remains as a restraining force -- for now," said Fawaz A. Gerges, director of the Middle East Center at the London School of Economics.
Syria's civil war has been bleeding into Lebanon for the past year, following similar sectarian lines of Sunni and Shiite camps. Overstretched and outgunned by militias, the military has struggled on multiple fronts in the eastern Bekaa valley and the northern city of Tripoli as armed factions fought street battles that often lasted several days.
In many cases, soldiers stood by helplessly and watched the violence.
On Monday, however, the army moved against al-Assir after his followers opened fire on an army checkpoint unprovoked.
Al-Assir, a 45-year-old bearded cleric who supports the overwhelmingly Sunni rebels fighting to topple Syrian President Bashar Assad, is an unlikely figure to challenge the Lebanese army.
Few had heard of him until last year, when he began agitating for Hezbollah to disarm, taking advantage of the deep frustration among Lebanon's Sunnis and a political void on the Sunni street following the 2005 assassination of former Prime Minister Rafik Hariri, a powerful Sunni leader.
Last year, al-Assir set up a protest tent city that closed a main road in Sidon for a month in a sit-in meant to pressure Hezbollah to disarm.
He kept local and international media entertained by pulling stunts such as riding his bicycle and getting his hair cut in public while he openly challenged and taunted Hezbollah like few had dared before. He even publicly criticized Hezbollah leader Sheik Hassan Nasrallah -- something few would do in Lebanon.