A man who had introduced himself as an IPS officer while intercepting a Trinamul student leader's car on Bijon Setu in February after it had apparently hit a pedestrian has been arrested on impersonation and extortion charges.

Cops picked up Soumen Kumar Suryabangshi, 29, from a flat in China Heights at Chinar Park of New Town early on Friday.

Suryabangshi had then said he was an additional superintendent of police from Jharkhand. But he has turned out to be a fraud who has studied only till Plus II, police said.

"Initially, a Kasba resident filed a complaint of extortion and harassment against him. Investigations revealed the allegations to be true. We found he wasn't a police officer," Vishal Garg, joint commissioner (special task force) and in charge of the detective department, said.

"We started a suo motu case against him. We have seized multiple fake police identity cards from him," Garg said.

Although the police refused to identify the Kasba resident who had filed the complaint against Suryabangshi, a source said he was the same Trinamul Congress Chhatra Parishad leader whom Suryabangshi had got arrested.

He had lodged the complaint with Kasba police station on October 18.

In February, the TMCP leader had been booked for causing death due to negligence in connection with running over a jaywalker on Bijon Setu. He had also been slapped with drink driving charges under the motor vehicles act.

Suryabangshi, originally from Jamshedpur, had been travelling on and off to Calcutta posing as an IPS officer of the Jharkhand cadre over the past few months, the police said.

He would roam all over the city in a vehicle with a "police" sticker and have a fake identity card of an IPS officer.

"He is unemployed. He would extort people by threatening to get them arrested if they refused to pay," Garg said.

The police, however, could not specify how many people he had extorted in the past few months.

After living in a rented flat in Kasba for sometime, he had recently shifted to Baguiati, the police said.

He has been sent to police custody for nine days.