In the second major strike by Maoists in Orissa in less than three weeks, 21 policemen were feared killed in a landmine explosion and firing by the ultras in Malkangiri district on Wednesday.

The van carrying the members of the Special Operations Group was on its way from MPV 126, 50 km from Malkangiri, to MPV-41, when the landmine went off.

''We suspect that all the 21 personnel in the van were killed in the incident,'' Director General of Police Gopal Chandra Nanda told PTI. The SOG personnel were ambushed by the Maoists, who felled trees to block the Kalimela-Motu road, to stop the vehicle.

When some of the policemen alighted to clear the road, they were fired on by the Maoists and their vehicle was damaged by the landmine explosion triggered at about the same time, police said.

Though the vehicle was not completely damaged in the blast, as it was an anti-landmine one, it overturned. When the policemen trapped inside it tried to come out, they were  gunned down by the ultras.

Security forces were rushed to the spot after the explosion that came 18 days after the Maoists carried out an audacious attack on a launch carrying elite anti-Naxal Greyhound police personnel of Andhra Pradesh in a reservoir in Malkangiri district. That incident had claimed 35 lives and injured dozens.

The southwestern range Deputy Inspector General of Police Sanjeev Panda said the van was an anti-landmine one and there were 21 personnel in it. He, however, did not confirm the casualty figure. "Our people are yet to reach the explosion site," he said.