Kolkata, Feb 2 (IANS): Former West Bengal Chief Minister and CPI-M leader Buddhadeb Bhattacharjee Sunday admitted that the Netai incident, in which nine people died, was a "grave mistake" committed by the party workers.

Nine people, including four women, were killed and 28 others were injured in the January 2011 clashes, triggered by assailants allegedly backed by the Communist Party of India-Marxist (CPI-M) in Netai near Lalgarh of West Midnapore district.

Reacting to the development, the state's ruling Trinamool Congress demanded the immediate arrest of Bhattacharjee for his party's complicity in the killings.

"The Netai incident was a mistake -- our lads committed a mistake, a big mistake in Netai," Bhattacharjee said while addressing a party rally in Midnapore of the district.

Bhattacharjee, who earlier had regretted the incident, however, accused the Trinamool Congress of unrepentantly carrying out atrocities on innocent people and rival party workers.

"We have committed a mistake, but what about them (Trinamool)? They have been carrying out atrocities all across the state. They have never regretted doing such acts," he said.

Reacting to Bhattacharjee's admission, Trinamool Congress leader and state Municipal Affairs Minister Firhad Hakim demanded immediate arrest of the CPI-M politburo member.

"When he has admitted his own men carried out the carnage, then he must be immediately arrested and tried before a court of law. Instead of trying to apologise, he should surrender himself immediately before the police," said Hakim.

Trinamool secretary general and Parliamentary Affairs Minister Partha Chatterjee ridiculed Bhattacharjee for his "apology".

"Considering the number of times he has apologised for the mistakes committed during his regime, he should be the Olympic champion for apologies. But people have realised and such apologies will not have any effect on them," said Chatterjee.