An “ultra-left” militant who was already on a security watchlist has been arrested for the devastating fire that gutted a 140-year-old city hall during ongoing riots across France, according to officials.

The 34-year-old suspect, known to police for acts of violence against public officials and currently on France’s national security watchlist, is suspected of starting the fire that gutted the 19th-Century landmark in the southwestern city of Limoges during Saturday’s violence, French media reported.

He was arrested on Tuesday morning in Val d’Issoire, about 30 miles from Limoges, according to French media.

Cops described him as an “ultra-left militant” who allegedly belongs to a violent radical-left group.

He is the “main suspect” in Saturday’s devastating arson attack, which saw the city hall’s clock tower and roof go up in flames before collapsing.

The listed building now needs a complete “Notre Dame-style” reconstruction, according to Limoges mayor Guillaume Guerin, who has threatened to resign if the French government doesn’t fund the rebuilding.

Almost 150 people arrested during the weekend’s nationwide protests have already been convicted and sentenced to prison for violence or property damage, officials announced on Tuesday.

Curfews were introduced in some French towns and cities on Monday, as fears remain that there could be a repeat of the violence next Saturday.