The seven persons came in two groups to Guwahati and were nabbed from Paltanbazar area of the city, a police spokesman said.
A three-member group came from Hojai in Nagaon district by train, while four others came in a vehicle and were scheduled to meet and discuss their strategy.
The arrested include the outfit's Commander-in-Chief Suber Sangma.
The outfit has its base in the Garo Hills bordering Bangladesh and some Lower Assam districts.