The encounter took place in the jungle near Khallari village under Borai police station limits this afternoon, a senior police official told PTI.
The dead jawan was identified as Assistant Commander S K Das, of 211 battalion of CRPF.
A CRPF team was carrying out a search operation in the area when it came under fire from Naxals. The ultras fled when CRPF retaliated, the official said.
Additional forces have been rushed to the spot to retrieve the body of the slain jawan, the official added.