Ratan, who had been declared wanted by police on June 2, was arrested from Keishampat Leimajam Leikai Community Hall in Imphal West district late last night.
Ratan, who has been spearheading a mass movement for implementation of Inner Line Permit System in the state, was picked up from the community hall where he was on a hunger strike with others, police said.
A district court remanded him to nine days' police custody today. The organisation and his followers protested against the 'wanted' tag on him and called a 48-hour strike from midnight tonight.
The police then alleged that Ratan was a member of the proscribed outfit United National Liberation Front and charged him with indulging in activities against the state and prompting social unrest. Ratan was absconding since then.