Additional Commissioner of Police Rajiv Kumar, who heads the STF, said: “They were arrested from an auction house, Parekh House on Lenin Sarani near Jyoti Cinema on Friday, where an auction was in progress.”

He added: “We have informed the Manipur police and are awaiting information from them. Only then we can claim that the arrested persons are militants.”

Police sources said the arrests are a major setback for extortion modules of Manipur militant groups operating in the city.

Sources said those arrested included PREPAK’s lieutenant K Kanta Singh and member of its finance department Achom Jagat Singh, and PLA’s finance department member M Chittaranjan Singh. They were present at the auction of old vehicles of the Border Road Task Force (BRTF) deployed in Manipur, to extort bidders from Manipur.

A cash amount of Rs 15 lakh was also recovered from them.

“A group of nearly 15 Manipuri militants had come to Kolkata in response to an open tender from the BRTF for auctioning old vehicles worth crores of rupees. The militants usually operate in two modules. The first actually participates in the bidding. The other waits on the sidelines for the bidding to finish and then extorts at least 20 per cent of the final bid amount from the bidders,” said STF sources.

“Both the PREPAK members belong to its “Shanti” faction. They have recently rechristened their faction as the United People’s Liberation of Kangleipak (UPLK) and Kanta Singh is one of its founder-members,” STF sources said. They added that the militants were living mostly in Madhyamgram in North 24 Parganas, close to the Dum Dum Airport. Chittaranjan Singh was staying in Room No 312 of the Manipur Bhawan on Rowland Road, sources said, adding that a team has been dispatched to Madhyamgram to conduct further raids.

The background of the five others, Chirom Iboyaima Singh, L C Deben Singh, Soram Tomba Singh, Koijam Ibomcha Singh, is yet to be confirmed but the security forces believe that they belong to the UPLK.