The bodyguard of Salafist cleric Sheikh Ahmed al-Asir, a Palestinian, was detained on Thursday at Beirut's Rafik Hariri International airport, media reports said.
Security agencies launched an investigation with Ali Abdul Hay, who was heading to an African country aboard Egypt Air.
According to the reports, Abdul Hay was detained at dawn.
Asir's supporters opened fire on an army checkpoint, late last month, leaving around 18 soldiers and more than 20 gunmen dead.
The gunbattles concentrated in the area of Bilal Bin Rabah Mosque and nearby buildings in Abra.
Asir, a 45-year-old cleric who supports the overwhelmingly Sunni rebels fighting to topple Syrian President Bashar Assad, is no where to be found along with Fadel Shaker.
Asir teamed up with Shaker, a onetime prominent singer, when around two years ago he began agitating for Hizbullah to disarm.