A policeman was killed and three others were injured when armed Maoist rebels attacked a police outpost at Bansjore in Jharkhand's Simdega district bordering Orissa.

The police said constable Sunil Kumar succumbed to injuries at a hospital in Rourkela in Orissa where three other injured policemen, including in-charge of the outpost, Amar Nath Paswan, are undergoing treatment.

"Nearly 500 Maoist rebels surrounded the outpost and hurled petrol bombs before firing indiscriminately around midnight last night. Policemen retaliated fire and the gunfight lasted till three in the morning," Sergeant Major J K Jha said.

Bloodstains were found in the area where the Maoists took positions indicating casualties on their side as well, the police said.

A civilian identified as a bus passenger was also injured in the attack, Jha said.

Before launching the attack, the Naxalites cut down a tree at Keriaghati and planted landmines to block police reinforcements reaching the outpost.