(Adds protest, interior minister comment)
By Oliver Holmes
BEIRUT, March 18 (Reuters) - Four Sunni Muslim scholars were beaten up in two separate attacks in Beirut on Sunday night, testing a fragile peace between the sects and factions that fought Lebanon's 15-year civil war.
Mazen Hariri and Ahmed Fekhran, both scholars at Lebanon's highest Sunni seat of learning, Dar al-Fatwa, were attacked by a group of men in the mainly Shi'ite Khandak al-Ghamik area after they left the Mohammed al-Amin mosque in downtown Beirut, security sources said on Monday.
Ibrahim Abdul-Latif and Omar Imani, also Sunni scholars, were assaulted in Shiyah, a Shi'ite district in southern Beirut.
The two main Shi'ite parties in Lebanon, the militant Hezbollah group and Amal, were quick to condemn the attacks and handed over five suspects to security forces, the sources said. They said the five men had been under the influence of drugs.
Lebanese Interior Minister Marwan Charbel later said that 10 men had been arrested.
The two-year-old conflict in neighbouring Syria - which pits mainly Sunni Muslims against President Bashar al-Assad, who comes from the Shi'ite-derived Alawite sect - has deepened divisions in Lebanon between some Sunnis and Shi'ites.
Lebanon-based political scientist Hilal Khashan said Syria could be implicated in the attacks as it had warned Lebanese groups not to support the uprising against Assad.
The extent of the injuries inflicted on the Sunni sheikhs was not clear, but a photo of two of them posted on Facebook showed one in a neck brace and the other with a bruised face.
Lebanon's civil war ended in 1990 but its political system remains based on sectarian allegiances and the country is plagued by occasional clashes between militant groups and vitriolic rhetoric from some politicians.
Lebanon's Grand Mufti Mohammad Rashid Qabbani said on Monday the attacks were the result of a "political war" by Sunni and Shi'ite leaders. He described condemnations of the perpetrators as insufficient and demanded swift action.
Prime Minister Najib Mikati, a Sunni, said on his Twitter account that the assailants would be held accountable as countrywide protests erupted on Sunday night.
On Monday afternoon, in the majority Sunni Beirut district of Tariq al-Jadideh, around 1,000 men gathered to protest the attacks. Prominent conservative cleric Da'i al-Islam al-Shahhal told the crowd that Lebanese state security and Shi'ite leaders had not made efforts to prevent the attacks.
"Why are these clerics being attacked when there are powerful groups controlling these (Shi'ite) areas," he screamed, waving his finger. Many protesters had long Sunni-style beards and booed and hissed when a speaker said the word "Shi'ite".
"These were two coordinated attacks. The fact that Hezbollah and Amal were quick to condemn the attacks means they wanted to dissociate themselves," Shahhal said. "There are those in the region that want to destabilise the country, such as the Syrian regime."
There was no immediate comment from officials in Damascus. (Editing by Jon Hemming)