Two children drowned while another went missing in a pond in the Chawkbazar area of the port city on Wednesday night, police said.
The identities of the deceased could not be known immediately.
Ferdous Hasan, officer-in-charge of Chawkbazar Police Station, said the three children had gone to take a bath in the pond belonging to a person, Omar Ali Matobbar, in East Sholoshohor and went missing.
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On information, drivers from the local fire service rushed to the spot and fished out the bodies of two children, aged about seven and five, respectively.
"Divers are searching for the missing child," the OC said.