An eight-year-old child was killed while four people were injured in a socket bomb explosion in front of a multi-storey building in the Nagerbazar area in Kolkata's northern suburbs on Tuesday, police said.

The explosion was reported outside a fruit shop on the ground floor of the building in the congested Kazipara area under the jurisdiction of Dum Dum Police Station around 9 am, a police officer said.

The National Investigation agency has reportedly sought details of the blast from the state CID.

The building also houses the office of South Dum Dum Municipality Chairman Panchu Roy, who claimed that he was the actual target of the blast.

Roy, stopping short of naming any political party, said the forces, which are currently attacking the ruling TMC all over Bengal, are behind the attack.

"It was a pre-planned blast... They had planned to kill me and other TMC workers, as it would create panic and help them gain foothold in the area," he told PTI.

He also claimed that the number of injured people was 10.

Asked whether the explosion was a result of infighting within the TMC, Roy said there was no such issue in south Bengal.