Thinking them to be balls, they picked up the crude bombs and started playing, police said. The bombs exploded, injuring the four children. Two of them are critical and undergoing treatment at the Malda Medical College and Hospital, police said.
While the other two boys are undergoing treatment at the local health centre, they said. Police said they are investigating to find who kept the bombs underneath a litchi tree beside the local mosque.
Superintendent of Police Amitava Maiti said police have cordoned off the area. The rest of the bombs will be detonated on Monday, he said.