In a daring pre-dawn swoop, armed naxalites Friday attacked a sub-jail in R Udayagiri town of Gajapati district and freed its prisoners, killing two policemen in the process, official sources said.

The naxals also took hostage Officer-in-Charge of the local police station Ranjan Kumar Mallick and Jailor Rabinarayan Sethi, the sources said.

Over 80 ultras, including women, attacked the police station, a nearby Orissa Special Armed Police camp, treasury, tehsildar's office and a telecom tower spreading terror in the town as they shot two policemen and injured two others, District Collector Binod Bihari Mohanty said.

Mohanty, who escaped the attack by taking refuge in a house, said police claimed three of the ultras, including a woman, were also killed when police returned fire.

However, the three bodies were taken away by the naxalites as they retreated, he said.

The exchange of fire continued for over two hours, Mohanty told PTI on the telephone adding, a large amount of arms had also been looted by ultras.

The ultras, who approached the town from two different directions, retreated via Saralapadar route towards the deep jungle.

The two policemen killed have been identified as Constable Prasanta Patnaik and Sentry Tuna Dehury, the sources said.

One of the injured policemen has been sent to MKCG Medical College Hospital at Berhampur while the other is being brought to Parlakhemundi for treatment at the district hospital, they said.

The police station had been totally ransacked by the naxalites who "pulled down" the gates of the sub-jail allowing prisoners to escape, the sources said.

The naxals had disconnected the telephone lines in most offices and also disrupted electricity supply in the town, they said.

Reports said around 50 prisoners, including some naxalites, were in the sub-jail, which has a capacity of 40. It was not known how many prisoners had escaped.

The attack, reminiscent of the naxalite raid on Koraput town three years ago, caught policemen by surprise at around 5.30 am. Many OSAP jawans had gone for jogging when their camp was attacked, the sources said.

Collector Mohanty said he had stayed overnight at the inspection bungalow of the revenue department at R Udayagiri after returning from a tour of Mohana area.

Police launched a combing operation in the area after the ultras retreated, he said.

Superintendent of Police, Gajapati, A N Sinha is on his way to the town with reinforcements, he added.

The naxalites had blocked entry to the town from different directions by felling trees and pushing boulders on the road.

Reports also said that the ultras may have planted landmines on the road to R Udayagiri town.