Preacher, who military prosecutors have sought the death penalty against after his followers killed soldiers, has been seized at Beirut airport

Gone was the long, scraggly beard of the fugitive sheikh’s heyday, replaced with a bushy moustache, thick glasses and the comb-over of a 70s actor. Ahmad al-Assir, a radical cleric whose followers battled the Lebanese army before he went into hiding two years ago, was seized at Beirut’s international airport over the weekend as he attempted to flee the country with the help of his new look and a forged passport.

Two years ago, Assir was riding a wave of popularity and notoriety. The charismatic preacher was a lonely voice speaking out against Hezbollah, the military and political organisation that dominates Lebanese affairs and has intervened to save President Bashar al-Assad’s regime from collapse in Syria.

The intervention has long angered Lebanon’s Sunnis, some of whom feel oppressed by the organisation’s ascendance and saw the Sidon-based preacher as a valve for their frustration. His supporters often clashed with local Hezbollah proxies, who sought to limit his influence in south Lebanon – site of the group’s traditional battlefront with Israel – and to reduce domestic opposition to involvement with Syria.

The tension boiled over in June 2013, when Assir’s men fired on an army checkpoint, killing soldiers and prompting a 25-hour military operation that turned much of Sidon into a battleground. Assir mysteriously fled as his forces were on the verge of defeat, going into hiding and issuing occasional messages urging Sunni soldiers to defect from the Lebanese military.

His recordings had little effect. The country has sought to limit the fallout from the Syrian war, with more than a million registered refugees adding to a pre-war population of more than 4 million. Many of the refugees are Sunni, upending the delicate sectarian balance of a country that lived through a 15-year civil war and an Israeli invasion.

The preacher’s saga came to a halt on Saturday morning, when Lebanon’s general security directorate announced it had arrested him as he was trying to board a plane to Nigeria, using a fake Palestinian travel document. Lebanese media circulated images of his physical transformation.

Military prosecutors have sought the death penalty against Assir for his role in the Sidon clashes.