Police also registered a case against Marad Municipal Corporation Vice Chairman and local Congress leader Antony Ashanparamabil in connection with the incident.
According to police, the gang had acted at the behest of Antony, named as the first accused in the case.
They were arrested for abducting the INTUC worker and torturing him after taking him to an unknown location in connection with a land case, police said.
The police move came within a week after they booked a ruling CPI(M) functionary here in connection with alleged threatening of a man over a business deal.
Police have registered a case under non-bailable offence against CPI(M) Kalamassery Area Secretary Zakir Hussain on a complaint sent to Chief Minister Pinarayi Vijayan by the victim, Jube Poulose, that he was threatened by Hussain and his gang over a business deal.
Vijayan, who also holds the Home portfolio, had said in the Assembly on October 25 that his government would not protect those people who indulge in criminal activities such as extortion racket.
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