Soon after the detention, a mob gathered outside and threw stones at the police station, demanding their release. They also ransacked the police station premises, officer in-charge's room and attacked the cops.
Five police officers were injured in the attack.
"Two youths had been arrested by the anti-rowdy squad of the police from the Chetla slum area on Monday night. They were identified from the CCTV footage of the police station," the officer said.
"Four more persons, including two women, have been detained and are being questioned over their roles in the attack," he said.
No action was initiated on Sunday against those residents of Chetla, considered to be a ruling Trinamool Congress (TMC) bastion. After the initial delay, a suo motu case was filed by the police on Monday.
Expressing displeasure, Kolkata Police Commissioner Anuj Sharma said the officer-in charge should have been strict and proactive in tackling the situation.
Condemning the incident, TMC Secretary General Partha Chatterjee demanded exemplary punishment for the accused. "This is unacceptable. How can people enter a police station and attack the officers on duty? There should be strict and exemplary action against the offenders to prevent the repeat of such things," Chatterjee said.
Criticising the Mamata Banerjee government, the Bharatiya Janata Party (BJP) said the incident again underlined absence of rule of law under the current regime. The state police would soon require central forces for their own protection, it added.
"It seems Banerjee's police would need central forces' protection against the onslaught of the ruling party," said state BJP chief Dilip Ghosh.