The arrested cadres are from the National Democratic Front of Bodoland (NDFB) faction opposed to peace talks with the government.
Additional Director General of Police (Law and Order) R M Singh said five cadres were arrested from Guwahati on Wednesday night, while two were later nabbed from Dimapur.
"All the arrested cadres are new recruits of the outfit and they were on their way to Myanmar for undergoing arms training at camps in the country," the police official said.
The NDFB's anti-talk faction, led by its leader I K Songbijit, has about 300 cadres at present. Police said it was carrying out fresh recruitment in Udalguri, Darrang and Sonitpur districts of Assam.
Meanwhile, George Lahiri, a 23-year-old cadre of the outfit, on Thursday surrendered before police. He handed over a pistol and four rounds of ammunition.
Police said he had joined the outfit in 2011 and underwent training in Myanmar for over two years.
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