A group of an estimated 400 Maoists on Saturday 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.

Police recovered bullet-riddled bodies of the 17 jawans in the jungles of Chattisgarh on the day, raising the death toll in the fierce gunbattle with Naxals the previous day -- the biggest massacre in more than a year that also left 31 injured.

Police also recovered the bodies of three jawans killed in the encounter, an official said, adding a search operation is on in the forest to trace a missing jawan.

Sources 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 (DRG) 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(PLGA) battalion no 1'-- Hidma-- and his associate Sujatha are suspected to be behind the Saturday 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 (LMGs) and used low-intensity improvised explosive devices (IEDs) 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.

The total approved strength of security forces personnel for the operation was 790 and the rest were taken as auxiliary and support elements for the long haul operation, the sources said.

"Inputs were received that Naxals were undertaking their Tactical Counter Offensive Campaign (TCOC) campaign in the Jagargunda-Jongaguda-Tarrem axis, and hence security forces teams from six camps were deputed to intercept them.

A CRPF Inspector is still missing, they said.

Officials said while maximum security forces personnel were killed due to bullet shots, one is suspected to have fainted and later died due to dehydration and other issues.

"The security forces personnel, especially CoBRA commandos fought very bravely and ensured that the Naxals could not prolong the ambush despite being at an advantage," the officer said.

About two dozen sophisticated assault weapons of the killed personnel are also stated to have been looted by the Naxals even as security officials said the search of the area is still on and details are being collected from the ground.

The dead include eight from the District Reserve Guard (DRG), seven from the CRPF's Commando Battalion for Resolute Action (CoBRA), six from the Special Task Force and one from the 'Bastariya' battalion of the CRPF," Inspector General of Police (Bastar range) Sundarraj P told PTI.

Union Home Minister Amit Shah on Sunday spoke to Chhattisgarh Chief Minister Bhupesh Baghel and took stock of the situation following the incident, officials said.

Shah also directed CRPF's Director General Kuldiep Singh to visit Chhattisgarh to assess the situation. He cancelled his election tours in poll-bound Assam after getting to know about the incident.

The operation was launched from five places - Tarrem, Usoor and Pamed (in Bijapur), and Minpa and Narsapuram (in Sukma), the official said.

The attack comes after the March 23 incident when five DRG personnel were killed as the Maoists blew up a bus carrying the security personnel with an IED in the Narayanpur district of the state.

On March 21 last year, 17 security personnel were killed in a Naxal ambush in the Minpa area of Sukma district.