The CBI wants to question the Kolkata Police Commissioner over missing documents linked to an investigation into the Saradha and Rose Valley chit fund scams over which several members of Mamata Banerjee's ruling Trinamool Congress have been jailed. Rajeev Kumar headed a Special Investigation Team probing the scams.

On Sunday evening, CBI officers were blocked from entering the Park Street home of Rajeev Kumar and detained at a police station for a few hours. "The Kolkata Police Commissioner is among the best in the world. His integrity, bravery and honesty are unquestioned," tweeted Mamata Banerjee.

The CBI says the police chief had been "missing" and had ignored several summons; he had skipped a meeting of the Election Commission on poll preparations. On Sunday evening, he joined Mamata Banerjee at the protest sit-in.

"The fact that paramilitary forces had to be deployed for the protection of those officers, who were diligently doing their duty, is for the first time an unprecedented view given to the citizen with regards to the state of anarchy in Bengal," said union minister Smriti Irani. She also questioned why a chief minister was protesting on behalf of a police chief.

The Chief Minister dared the centre to place Bengal under President's Rule and railed at the CBI's attempt to doorstep the police chief. "How dare you come to a police commissioner's home without a warrant? Mr (Ajit) Doval is doing whatever PM wants him to do, he is the one giving all the instructions to CBI," referring to the National Security Advisor.

The CBI told the Supreme Court this morning that the Kolkata police chief is a "potential accused" in the investigation into the chit fund scams in Bengal, accusing the city police of destruction of electronic evidence. The Supreme Court asked the investigating agency to produce evidence to support its allegations; it will take up the petition tomorrow. The Governor has sent a confidential report on the incident to the Home Ministry.

In the evening, Ms Banerjee handed over awards to police officers at the dharna spot. Answering critics who asked why she was upset over the questioning of a police officer, she said, "I did not take to the streets when you touched TMC leaders. But I am angry when they tried to insult the chair of the Kolkata Police Commissioner, he is leading the organisation".

The latest showdown follows an intense turf war between the BJP and Mamata Banerjee as the country heads to polls. Over the past few weeks, the Chief Minister has blocked attempts by the BJP to take out roadshows and even denied permission to top leaders to land their choppers at rally sites.

Mamata Banerjee accuses the BJP of going after her administration with greater verve after her mega rally of 23 opposition parties in Kolkata last month. She has also accused PM Modi of using unparliamentary language in his recent rallies. The Prime Minister had said the Bengal government was killing the aspirations of the middle class through "Triple T - Trinamool Tolabazi Tax". Tolabazi roughly translates to an act of organised extortion.