Sixteen soldiers have been killed in clashes with supporters of a radical Sunni cleric in southern Lebanon, the army said Monday, in violence tied to rising sectarian tensions fanned by the Syria conflict.
The fighting began on Sunday on the outskirts of the city of Sidon and intensified on Monday, residents and local media said.
The security cabinet, including Lebanon's army chief, met in emergency session and pledged the military would fight until it "finishes with" Salafist Sheikh Ahmad al-Assir.
A military judge issued a warrant for the controversial cleric's arrest, a judicial source said.
The violence is among the worst in Lebanon since the start of the Syrian conflict, which has inflamed sectarian tensions in the country, particularly between Shiite supporters of the Damascus regime and Sunni backers of the uprising.
Media warned that Lebanon "finds itself before a decisive test," evoking the spectre of the devastating 1975-1990 civil war.
The violence erupted on Sunday, when Assir supporters fired on an army checkpoint.
Witnesses said the fighting worsened on Monday, reporting heavy gunfire and the sound of mortar and rocket fire in the Abra neighbourhood on the eastern outskirts of the coastal city.
"The clashes are very violent, we can hear intense rocket fire and gunfire every few minutes," an Abra resident told AFP.
The army said 16 soldiers had been killed since the fighting began, and medical sources reported at least 35 wounded, mostly civilians.
The government said Tuesday would be a day of mourning for the dead soldiers.
A source close to Assir said at least five of his supporters had also been killed.
Two Islamist groups in the Ain al-Helweh Palestinian refugee camp -- Jund al-Sham and Fatah al-Islam -- joined the fighting, firing at an army post on the edge of the camp, a security source told AFP.
Assir's brother said the cleric and his supporters were inside Abra's Bilal Bin Rabah mosque, where Assir preaches, with the National News Agency saying the army was "metres" (yards) away.
"There has been a decision taken to finish us off, but we're resisting up until now," Amjad al-Assir told AFP by phone.
"Sheikh Assir will stay in the mosque until the last drop of blood."
After the emergency meeting, the security cabinet said the army "has a duty... to continue its operations until it finishes with the armed men, brings (Assir's) headquarters under control, and arrests the army's attackers".
The army issued a statement urging gunmen to "lay down their arms and surrender immediately".
Assir was a virtual unknown before the conflict in Syria began in March 2011, but has made headlines for his vocal criticism of Lebanon's Shiite group Hezbollah and its alliance with the Syrian regime.
He has accused the Lebanese army of backing the powerful movement and turning a blind eye to both its weapons and its dispatch of fighters to battle alongside Syrian troops against rebels.
Assir has also encouraged his followers to head to Syria and join the Sunni-led uprising against President Bashar al-Assad.
In Syria, meanwhile, Foreign Minister Walid al-Muallem warned that Assad would not resign or hand over power at a peace conference slated to take place in Geneva.
"President Bashar al-Assad will not resign. If your condition (for talks at Geneva) is President Assad's resignation, don't bother coming," he told a Damascus news conference.
Muallem said the government was open to the creation of "a broad national unity government" but slammed nations that back the rebels for pledging to arm them.
"This will only prolong the crisis," he warned.
The violence in Sidon, which follows a clash between Assir's supporters and Hezbollah backers last week, prompted a military judge to issue an arrest warrant for the cleric and 123 of his supporters.
The fighting left terrified civilians stranded, and the National News Agency published an appeal by Abra residents urging security forces to evacuate them.
On Sunday, Assir issued a video message saying he was being "attacked" by the military, which he described as "sectarian" and accused of supporting Hezbollah chief Hassan Nasrallah.
He urged soldiers to desert and protesters to block streets, a call heeded by some in the majority-Sunni northern city of Tripoli, the scene of regular fighting between pro- and anti-Syrian regime residents.
An AFP correspondent said masked gunmen deployed in the central Nur Square, blocking roads with burning tyres before throwing several hand grenades and causing panic.