Security forces apprehended four Maoist cadres and recovered arms and ammunition in Assam's Tinsukia district on Saturday night, police said on Sunday.
Acting on a tip-off, police had launched a search operation at Chabua area in the district along the Assam-Arunachal Pradesh border and nabbed the rebels.
The arrested Left wing cadres were identified as Anup Hazarika, Ritul Das, Dhiraj Dihingia and Biraj Sutradhar.
Police recovered one 9mm pistol with magazine, five rounds live ammunition and extortion notes in possession of them.
Meanwhile, a United Liberation Front of Asom (ULFA) militant who had surrendered was killed and a police officer injured in a gun battle in Dibrugarh district on Sunday.
The encounter took place at Khowang area in the district, where a police team had launched a search operation.
"Based on intelligence report, when we reached the area, a militant group started firing on the troops and bullets were exchanged," a police official said.
During the gun battle, a ULFA militant who had surrendered was killed on spot and a police officer injured.
"The militant group managed to escape from the encounter spot," police said.
The slain militant was identified as Papul Thakuria and the injured police official named Utpal Bora were rushed to the nearest hospital.
Security forces recovered a motor bike and some incriminating documents from the spot.
(Reporting by Hemanta Kumar Nath)