The incident occurred at 9:40am when the policemen were moving for an operational task in the forest between Pavimuranda and Murmuri villages in Chamorshi taluka of the district.
Officials said the slain security personnel belong to the specialized C-60 anti-Naxal operations force of Maharashtra and the blast took place when their vehicle was moving along the Murmuri-Chamuri axis of the district.
"We have lost seven of our men in the attack carried out by Naxalites. The incident occurred in Gadchiroli," a senior police officer said.
The injured have been airlifted to Nagpur while additional reinforcements of security personnel have been sent, they said.
After the landmine blast, there was an exchange of fire between the police and Maoists.
Firing is still going on in the forest area, police said.