Sikkim police on Tuesday arrested Dhiren Boro, vice president of the banned National Democratic Front of Boroland and one of Assam's most prominent militant leaders in capital Gangtok.
The NDFB top gun fell into the police dragnet after the arrest of two suspected NDFB rebels from a forest in Alipurduar in North Bengal on Tuesday.
They also arrested his wife, Pratima, who is a trained activist of the outfit, and two other associates identified as Babloo Sargari and Prabin Boro.
Boro and his wife had been apparently living in Sikkim, considered a haven for rebels looking for shelter, under a false identity for the past one year.
He has been booked under four sections of the Prevention of Terrorism Act, the first time the law is being used in Sikkim.
Boro, wanted in several cases in Assam, had been on the run from police and security forces for nearly a decade.
According to the police, he had been living in a rented flat in the flour mill area at Tadong for the last one year.
Guwahati Inspector General of Police (special branch) Khagen Sharma said a police team would leave for Gangtok on Friday and take the arrested leader into custody and bring him to the state for interrogation.
Boro has been associated with the NDFB outfit since its inception and is considered a to be the brain behind the outfit.
The special operations unit of the Assam police had, on November 26, 2002, arrested NDFB general secretary Gobinda Basumatary at Rangiya railway station in Kamrup district.
Boro had been living there with his wife and their two children.
The NDFB vice-president was last arrested by the army in 1993, but had been released on bail.