At least seven policemen were seriously injured this evening when naxalities trigerred a landmine blast at Deorlitola village in Gondia district of Maharashtra, police sources said.The police party, consisting of two sub-inspectors and seven constables, was returning from Kadwanda Dam, some 30 kms from the district headquarters, when their vehicle was blown up by the landmine on the Deori-Chichgad road, Special IG Police (Nagpur Range) S M Mushrif said.