Daring Chief Minister Mamata Banerjee to ask for a CBI probe into the lynching of a college student, the Congress on Sunday said it will observe a statewide shutdown on August 20 against the "growing anarchy" in West Bengal.

Krishna Prasad Jana, a student of Sabang Sajanikanta Mahavidyalaya in West Midnapore district, was beaten to death on Friday during a clash in the college.

"I dare the Chief Minister to ask for a CBI probe into the lynching. Even before police began investigating the case, she had given her conclusion. If she is so much confident, then let the CBI probe the case," state Congress president Adhir Ranjan Chowdhury said.

The Congress MP was referring to Banerjee's comments that Jana's death was a result of internal feud among Congress-affiliated Chhatra Parishad activists.

While a police complaint has been filed against six people for Jana's killing and three have been arrested, Superintendent of Police Bharati Ghosh said those named in the complaint and the arrested were not involved in the attack.

"None of the six whose names figure in the FIR were seen wielding lathis. There is no such video footage featuring the three arrested also," said Ghosh.

Criticising Ghosh for "towing the Chief Minister's line", Chowdhury said the Congress would observe a shutdown on August 20.

"There is no justice, no rule of law in the state. Under this regime, there have been repeated incidents of rape, murder and lawlessness across the state," he said.

Meanwhile, the ruling Trinamool Congress ridiculed Chowdhury's shutdown call.

"It is a democracy and anybody can call a shutdown. But it is to be seen whether it will be a shutdown or turn out to be a joke," Trinamool leader and Panchayat Minister Subrata Mukherjee said.