"Gopal Tewari was arrested from a hotel at Baguihati this evening," a senior police official told PTI.
Police were on the trail of Tewari since the incident on April 18 soon after the civic polls got over. Sub-Inspector of Girish Park police station Jagannathan Mondal was injured in the attack.
Police earlier seized a huge cache of arms and ammunition from Tewari's residence.
Four persons have been arrested in the case so far.