Rallies and counter rallies over the arrest of TMC leader Anubrata Mondal in a cattle smuggling case kept West Bengal's political cauldron on the boil on Friday with the state's ruling party questioning the impartiality of the probe agency and the opposition camps celebrating the triumph of "good over evil".

The Central Bureau of Investigation (CBI) on Thursday morning arrested Mandal from his residence in Bolpur area of Birbhum district, for allegedly not cooperating in its probe into the cattle smuggling case. He was later remanded in 10-day custody of the central agency by a special CBI court.

The TMC took out protest rallies in various parts of the state on Friday, accusing the CBI and Enforcement Directorate (ED) of acting as "frontal organisations" of the BJP at the Centre.

Carrying posters and placards, TMC's student and youth wing members rallied in various parts of the state, demanding unbiased probe by the ED and the CBI.

"We have serious doubts about the way central agencies function. We have seen that they maintain silence when it comes to taking action against BJP leaders facing allegations of corruption," Trinamool Congress Chatra Parishad (TMCP) state president Trinankur Bhattacharjee said.

He claimed that the central agencies go slow when it came to graft cases against BJP leaders.

"What about similar cases against BJP leaders, or those who have joined the saffron camp to escape the clutches of investigating agencies," he sought to know.

The protest rallies were taken out in several districts of the state, including Mondal's hometown in Birbhum, as well as East Midnapore, West Midnapore, Purulia, Siliguri, Bankura and Calcutta.

Meanwhile, the opposition BJP, the CPM and Congress organised counter rallies in various parts of the state, rejoicing the arrest, and stating that the day was not far when the entire top brass of the ruling TMC would be behind bars on corruption charges.

The arrest of Partha Chatterjee and Anubrata Mondal are just the beginning," BJP national vice-president Dilip Ghosh said, while addressing a rally.

Senior TMC leader and minister Partha Chatterjee was arrested on July 23 by the Enforcement Directorate in connection with a school recruitment scam.

State Congress president Adhir Ranjan Chowdhury said the arrest of TMC strongman Mondal symbolises the victory of "good over evil".