At least 12 people were killed in fierce clashes in the Lebanese city of Sidon on Sunday, June 23, between the army and followers of a Sunni Muslim cleric who have been caught up in sectarian fighting fuelled by the war in neighboring Syria, Reuters reported.

Guns and rocket fire rattled the port city 40 km (28 miles) south of Beirut that has been on edge since violence erupted there last week between Sunni and Shi'ite Muslim fighters, at odds over the Syrian conflict.

Lebanese authorities have been trying to quell the fighting and Sunday's clashes began when police arrested a follower of hardline cleric Sheikh Ahmed al-Assir at a checkpoint, sources in the city told Reuters.

Other Assir backers attacked security forces in the city in retaliation and called on their supporters to come out onto the streets across Lebanon.

Ten soldiers were killed and 40 wounded, a security source said. At least two Sunni gunmen were killed and 13 wounded, he added.

Syria's conflict, pitting mainly Sunni rebels against President Bashar al-Assad, an Alawite from an offshoot of Shi'ite Islam, has strained fragile sectarian relations in Lebanon and triggered clashes in Sidon and other cities.

Tensions have mounted since the Lebanese Shi'ite militant group Hezbollah sent fighters over the border to back Assad.

The Lebanese army launched a crackdown in Sidon and sent troops to potential hot spots across Beirut, aiming to stop clashes spreading to the capital.