The CRPF jawan, Sachindra Sharma, fell to the Maoists' bullets while security forces gunned down two ultras during the exchange of fire, Additional Director General of Police (ADG), Headquarters, Ravindra Kumar said.
The slain jawan of CRPF's 159th battalion was posted at Gaya, he said.
The encounter took place between the security forces and the armed Maoists after the CRPF's CoBRA battalion, STF and Gaya police launched a joint combing operation in Balthar forests this morning following a tip-off, Kumar said.
The armed Maoists opened fire and triggered several land mine blasts to stop the advancing security forces, who retaliated, triggering the gunbattle.
Two ultras were killed during the hours-long encounter, which began at 6 am, the officer said, adding that the security forces detected blood stains at several places in the forest which indicated that several other ultras may have also died or suffered injuries.
"The retreating Naxalites might have dragged the bodies of the deceased or taken away injured colleagues," the ADG said.
Nine security men, including two civilian policemen, were injured in the encounter.