Arabul was taken into custody on the Eastern Metropolitan Bypass, district police superintendent Pravin Tripathi told IANS.
Mollah, a former minister and a senior legislator, was severely beaten up by Trinamool workers led by Arabul Jan 6 when he went to Bamanghata area where a Communist Party of India-Marxist office had been damaged.
Mollah was admitted to hospital with multiple injuries. The attack caused a political uproar.
The disturbances stretched to Jan 8 when a number of political activists were injured in firing and clashes between the Trinamool and CPI-M.
Governor M.K. Narayanan had said: "This is not a good political culture. I think some sort of goondaism is going on here."