Acting on a tip off, Hadar was arrested from Balipathar market on the Assam Nagaland border on Sunday, the police said.
Hadar, based in Khanapara along the Assam and Meghalaya border in Ribhoi district, was involved in the kidnapping of a businessman on November 16 from Umiam near the state capital, who was released later after paying a huge ransom to the outfit, Ribhoi district police chief C A Lyngwa told reporters.
Hadar, who was booked under Meghalaya Preventive Detention Act earlier and released in 2010, was allegedly involved in transhipment of arms for the outfit from Dimapur via Assam to Meghalaya, Lyngwa said.
While no arms was seized from Hadar, Rs 2 lakh was seized from his possession.
Others who were arrested were Karmeshwar Sangma who was arrested from Nongpoh and his brother Imanuel who was arrested from Nongstoin along with his aide, a Mizo youth.
Another youth, Kamal Hossain, who was his sympathiser was arrested from Chandmari in Guwahati on Saturday.
The arrested were produced in court today and were remanded to 14 days police custody.