Bodoland People's Front leader and executive member of Bodoland Territorial Autonomous District Council Mono Kumar Brahma was remanded to 14-day judicial custody by the court of the chief judicial magistrate in Kokrajhar on Monday.
The BPF leader was later admitted to Rupnath Brahma Civil Hospital in Kokrajhar after he fell ill.
He was arrested on Saturday morning by the police after the recovery of two AK-47 assault rifles and 60 rounds of ammunition from his residence during an early morning raid.
Meanwhile, curfew was relaxed for eight hours, from 8 am to 4 pm on Monday, in violence-hit Kokrajhar district as there was no fresh incident of violence during the last 24 hours, according to the police.
But indefinite curfew remained enforced in five villages -- Nalbari, Ziaguri, Tiplabeel, Tintila and Alurbhui -- in Kokrajhar sub-division of the district and four villages including Subkata Part I, Number 2 Bajou Gaon, Howriapet and Bhumka in Gossaingaon sub-division.
The arrest of the BPF leader has severely threatened the seven-year long alliance between the BPF and the ruling Congress in Assam.
BPF chief Hagrama Mohilary has termed the arrest of party leader Mono Kumar Brahma as part of a deep-rooted conspiracy against the BPF and stated that the party was ready to walk out of the alliance with the Congress if the latter asked it to do so.
On the other hand, Assam Chief Minister Tarun Gogoi stated that it was up to the BPF to decide whether to continue its alliance with the Congress.
The ruling Congress has 78 Members of Legislative Assembly in the 126-member Assam assembly while its ally BPF has 11 MLAs.