NAGPUR, February 27: A police sub-inspector was seriously injured when Naxalites of the outlawed People's War Group of CPI (ML) opened fire on a police party in the forests between Hemalkasa and Koingunda in Gadchiroli district, bordering Andhra Pradesh here yesterday.The police party, patrolling the forests as part of the anti-Naxalite operations, sighted a group of 10 to 15 Naxalites in the forest abut five kms from Bhamragadh police station.The Naxalites opened fire after they were ordered to surrender. Police immediately retaliated, according to a report received here today.PSI Matke was rushed to a government medical college at Nagpur.Earlier, too security forces have had to battle it out with Naxalites in forests of Gadchiroli district. Fatalities have been quite severe.