At least 12 Maoists have been killed in the massive anti-Naxal operation launched jointly by security forces of Jharkhand and Orissa since Saturday in Saranda forest, a top police official said on Monday. Jharkhand Director General of Police Neyaz Ahmad said that ten to 12 Maoists have been killed since Saturday.Meanwhile, the Maoists blew up a hostel and panchayat bhawan at Anandpur and triggered three landmine blasts in the Tirilposhi jungle today morning.