A group of an estimated 400 Maoists had ambushed security personnel who were part of a large contingent deployed for a special operation, leading to the killing of at least 22 personnel and injuries to 30 others, official sources said on Sunday

They said the contingent of about 1,500 troops drawn from CRPF'S specialised jungle warfare unit CoBRA, some teams from its regular battalions, a unit of its Bastariya battalion, the Chhattisgarh Police affiliated District Reserve Guard and others had launched a search and destroy operation along the border of Bijapur-Sukma district around noon after they got inputs of some Maoists presence in the area.

At least 400 Naxals, an officer said, led by the most wanted Maoist commander and leader of the so-called 'People's Liberation Guerrilla Army battalion no 1'-- Hidma-- and his associate Sujatha are suspected to be behind the Saturday's ambush that took place in an area that is a strong-hold of the ultras due to the difficult terrain, large tracts of forests and less number of security forces camps.

The Maoists rained bullets from light machine guns and used low-intensity improvised explosive devices to mount the attack that went on till evening.

He said that the Maoists carried their dead, estimated to be about 10-12, on tractor trolleys.