Calcutta, April 18: A police officer took a bullet under his collarbone in north Calcutta an hour after polling ended, marking a bloody end to a corporation election that stood out for complete domination of Trinamul in booth "management", slow-burn aggression and a blizzard of complaints of foul play.

The gunshot injury to Jagannath Mondal, a sub-inspector with Girish Park police station, was all the more startling because through the day the police were accused of shielding Trinamul supporters who were allegedly manipulating the polls.

Chief minister Mamata Banerjee, who visited the officer in hospital along with police commissioner Surajit Kar Purkayastha, said: "Calcutta police is the man of the match. I thank and congratulate my entire Calcutta police family."

Mondal, 55, was shot at when his police posse tried to disperse a group, allegedly led by the husband of the Trinamul candidate in Girish Park, that had attacked the house of a Congress leader and stormed a Congress election kiosk.

Congressman Bikash Yadav's wife alleged that a Trinamul group had told the family in the morning " vote-er por dekhe nebo (we will teach you a lesson after the voting ends)". She said the group carried out the threat after polling ended and attacked the house.

Vinod Yadav, a resident who identified himself as a Congress supporter, said: "Sanjay Bakshi was leading the Trinamul mob that went on the rampage. They were carrying iron rods and firearms." The group had split into two and attacked the police.

Bakshi is a former Trinamul MLA and husband of the Trinamul candidate from Ward 25 (Girish Park).

Bakshi was not available for comment. His son Joy, also a Trinamul leader, said neither his father nor the party had anything to do with the attack. "Trinamul is in no way involved. The Congress and the BJP are behind all this. They had put up a roadblock in the area and it led to the trouble," he said.

Officer Mondal was taken to a nursing home and shifted to the Calcutta Medical Research Institute (CMRI). Tonight, his condition was stated as critical but stable.

An officer said the police squad was attacked from the front and the rear. "We were chasing the group in the front when someone fired. The bullet hit Mondal," said the officer.

"Mondal's scapula (shoulder bone) has been pierced and the bullet is lodged inside. We are still discussing if a surgery is needed to extract the bullet," said a doctor.

Mondal's wife Maya and daughter Atashi visited him in hospital. Maya took ill and had to be administered medicines.

Mamata reached the hospital in the evening and stayed for around 30 minutes. "She assured us of all help. She told us that the doctors had told her he was out of danger, which was very assuring," said Somen Nath, a cousin of Mondal.

In 2013, sub-inspector Tapas Chowdhury was shot dead in front of a college in Garden Reach. The then Trinamul councillor, Mohammed Iqbal, is the prime accused.

Chowdhury's daughter Tanushreesaid this evening: "Some things just don't change in Calcutta. I think this hooliganism that is associated with elections will never change.... Sub-inspector Mondal has been taken to the same hospital where they took my father. I hope he gets well."