Bhubaneswar, May 1: Security forces have stepped up their combing operation on the Kalahandi-Nabarangpur border following yesterday's encounter between the Special Operations Group (SOG) and Maoists at Ampani village in which three rebels, all of them women, were killed.

Police had found three .303 rifles, one 9mm pistol and some indigenous explosive devices from the encounter spot.

Sources said that more forces have been rushed to the area to assist the SOG and district voluntary force (DVF) jawans in carrying out the combing operation.

"We are combing the entire forested area on the border in order to flush out the rebels. Similar operations are also being carried out in other Maoist-dominated areas of the state," said a senior police officer.

The rebels, who are trying to make forays into new areas, have been active in Kalahandi and Balangir districts over the past few years. These districts are considered sensitive because of their predominant tribal population. A major alumina refinery is also located in Kalahandi district which, along with Balangir, also shares borders with Rayagada.

Sources said the rebels were determined to block all development activities in Kalahandi and its nearby areas. They are also taking advantage of the fact that local Kondh tribals are up in arms against the alumina refinery run by a major industrial house.

The Maoists have also been active in Rayagada, Kandhamal, Koraput and Malkangiri districts, all of which have a sizeable tribal population. While they have targeted BSF jawans posted in Koraput and Malkangiri several times in the past, they are up against the CRPF in other areas.

The state police officials have been trying their best to co-ordinate between the central paramilitary forces and the local police to ensure best possible results in their operation against the rebels who also sneak into Odisha from the neighbouring Chhattisgarh and Andhra Pradesh states.

"The major threat comes from the Chhattisgarh cadres who, after every major operation in the neighbouring state, sneak into Odisha where they have several hideouts. We are also in touch with the Chhattisgarh police to tackle the threat of Maoist violence," said a senior police officer.

The other major area of worry for the state police is its border with Jharkhand on the Sundargarh side where the Saranda forests provide a safe sanctuary to the rebels.

The rebels, who had been flushed out of the area four years ago in a joint operation by Odisha and Jharkhand police, are back in Saranda.