Two persons died and seven others were injured as an under-construction five-storeyed building collapsed in the Garden Reach area of Kolkata, city mayor Firhad Hakim said on Monday.

Hakim apprehended that some more people might still be trapped under the debris.

The rescue operation is going on at the site located at Azan Molla Lane in the city's western periphery.

"In a horrific accident, an under-construction five-storeyed building collapsed around midnight. Two persons were killed and at least seven people were injured," Hakim said.

At least 10 people were rescued from the site, an official said.

The city mayor said there were still a few persons trapped under the debris and efforts were on to rescue them.

The injured were admitted to a hospital, Hakim said.

He announced an ex-gratia of Rs five lakh to the next of kin of each deceased and Rs 1 lakh to injured persons.

Hakim, who is also West Bengal's urban development minister, said "I have spoken to Chief Minister Mamata Banerjee and we will give Rs five lakh to the next of kin of each deceased person and Rs one lakh to each injured person." Kolkata Police Commissioner Vineet Goyal visited the spot and took stock of the rescue operation.

"The under-construction building collapsed in the Garden Reach area late on Sunday night. We have rescued a few people. The recuse operation is still going on," a police official said.

Ambulances were stationed at the spot.

According to locals, who were the first responders, concrete chunks fell from the building before it collapsed.

There was a loud sound and a thick cloud of dust engulfed the area as the building collapsed. The debris fell on nearby shanties in the densely populated area, they said.

"Although no one lived in the under-construction building, it collapsed on the adjacent shanties. We fear that many individuals might still be trapped under the rubble," said a local resident.

In a post on X, Leader of Opposition in the West Bengal Assembly Suvendu Adhikari said, "I urge @chief_west, Secretary @HomeBengal, @CPKolkata to immediately involve West Bengal State Disaster Management Team for immediate Rescue & Relief." "I am receiving frantic calls regarding probable casualties. Please dispatch any team which can help in rescuing the victims, be it Fire Servicemen, Police or any other team," he said.

Adhikari also shared pictures from the building collapse site.