Modi-Shah trying to organise coup in West Bengal: Mamata Banerjee

She also alleged that National Security Advisor Ajit Doval was directing the CBI to harass political opponents, as per orders of the prime minister.

"I feel ashamed to talk to such a prime minister who has blood on his hands," she said.

"Narendra Modi and Amit Shah are trying to organise a coup in the state as we had organised the opposition rally on January 19. We were aware that the CBI will attack us after we organised the rally," Banerjee said, referring to the Brigade rally attended by leaders of about 20 opposition parties.

Banerjee said the CBI's action is politically vindictive. "Our government arrested chit fund owners when we came to power. It is we who formed an SIT to probe the matter," she said in a hurriedly-called press conference outside Kolkata Police Commissioner Rajeev Kumar's residence.

She said she would stage a dharna in central Kolkata tonight.

In an unprecedented development, a number of CBI officers, who had gone to question Kolkata Police chief Rajeev Kumar in connection with chit fund scam cases, were bundled into police jeeps, whisked to a police station and detained on Sunday.

Amidst escalating tension between West Bengal Chief Minister Mamata Banerjee and the Centre, Loudon Street in central Kolkata witnessed a virtual showdown between the state police and the CBI.

There were conflicting reports about some CBI officers being arrested. While the agency sources claimed that some of its men were forcibly taken away from Kumar's Loudon Street residence and arrested, a senior police officer denied the claim and said they have been taken to the police station to check if they had the documents required for questioning Kumar.

As politics played out on the street, West Bengal Chief Minister Mamata Banerjee rushed to the residence of Kumar. She had earlier extended her support to Kumar and alleged that the BJP was "misusing power to take control of the police and all other institutions".