A Lebanese military tribunal has sentenced a radical Sunni cleric to death for leading an armed group that clashed with the country's army four years ago in battles that killed 18 soldiers.

Thursday's verdict comes two years after Ahmed al-Assir has been put on trial. He was convicted of illegal possession of firearms and killing soldiers.

A famous singer who supported al-Assir was sentenced in absentia to 15 years. The sentence can be appealed.

Al-Assir's group clashed with troops in 2013 in Sidon, a southern port city, in fighting that escalated tension between Sunni and Shiite Muslims who support opposing sides in neighboring Syria's civil war.

Al-Assir is vehemently opposed to Lebanon's powerful Shiite militant Hezbollah group. During the trial, he refused to recognize the court's authority.