Mannan, an adviser to the BNP chairperson, was arrested in Dhaka on February 11, 2015 for his suspected involvement in an arson attack on a passenger bus in Gazipur on February 4.
He came out of Kashimpur Jail around 1pm on Friday. Leaders and activists of BNP and its associate bodies greeted Mannan at the jail gate after his release.
Senior Jail Super Subrata Kumar Bala of Kashimpur Central Jail-1 said Mannan was released after the authorities had scrutinised the documents of his bail from the High Court.
After Mannan was arrested in the arson case in February 2015, Panel mayor Asadur Rahman Kiron was made the acting mayor upon a court directive the next month.
Police have pressed charges against Mannan in two cases. The government suspended him in August 2015.