Kolkata campus violence: Trinamool Congress leader arrested from Bihar

"Iqbal has been arrested from Dehri-on-Son. He will be brought to Kolkata," said Shibaji Ghosh, Additional Director General, CID. He will be produced before a Kolkata court where the CID will seek his transit remand from the court, added Mr Ghosh.

Mr Iqbal is charged with rioting, attempt to murder and certain sections of the Arms Act by police. The CID, which subsequently took over the investigation, had been looking for Mr Iqbal for almost a month.

Video footage aired by television channels showed Mr Iqbal standing next to a man called Sheikh Shubhaan when the latter fired the bullet that the police say killed the Sub Inspector. Mr Shubhaan was among 12 people who were arrested within two days of the violence.

The violence in the college erupted over the issue of picking up nomination forms for the students' union election.  The cop was shot dead while trying to break up the clashes.

Two days after the clash, West Bengal Chief Minister Mamata Banerjee removed Kolkata's police chief RK Pachanda and said she was angry that people named in the FIR had not been arrested.

Ms Banerjee's detractors had alleged that Mr Pachanda was removed as Commissioner because he wanted to arrest some members of her party in connection with the policeman's death. Mr Iqbal is known to be close to the state's Urban Development Minister Firhad Hakim, who in turn is close to the Chief Minister.

Mr Hakim had defended Iqbal saying "he was not involved".

Several opposition leaders and the state's Governor MK Narayanan had slammed Mr Hakim's alleged attempt to shield Mr Iqbal.

The Trinamool Congress has alleged that a man named Mokhtar, who reportedly has Congress links, is responsible for the policeman's death.

The Congress has demanded an investigation by the Central Bureau of Investigation (CBI).