BEIRUT — Lebanon’s third-largest city was turned into a battle zone Monday as the military battled heavily armed followers of an extremist Sunni cleric holed up in a mosque in a southern port city.
Residents fled as machine gun fire and grenade explosions shook the coastal area in one of the deadliest rounds of violence, seen as a test of the weak state’s ability to contain the furies unleashed by Syria’s civil war.
At least 16 soldiers were killed in two days of clashes with armed followers of Ahmad al-Assir, a maverick sheik whose rapid rise among the ranks of some Sunnis is a symptom of the deep frustration among many who resent the Hezbollah-led Shi’ite ascendancy to power in Lebanon.
The fierce fight that 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 Hezbollah.
‘‘Sidon is a war zone,’’ said Nabil Azzam, a resident who returned to Sidon briefly Monday to check on his home after having fled a day earlier with his family. ‘‘This is the result of all the sectarian rhetoric that has been building as a result of the war in Syria. It was bound to happen,’’ he said by telephone, his speech interrupted by a burst of gunfire.
The fighting in Sidon is the bloodiest involving the army since the military fought a three-month battle in 2007 against the Al Qaeda-inspired Fatah Islam group inside the Palestinian refugee camp of Nahr el-Bared in northern Lebanon.