Anar was last seen leaving Biswas's home for a doctor's appointment on May 13 but failed to return as scheduled, prompting Biswas to file a missing persons report on May 18.

Anar traveled to West Bengal for medical treatment on May 11 but disappeared from Kolkata on May 13.

Anar, a three-time parliamentarian and president of Awami League's Kaliganj sub-district unit, vanished during a personal visit to Kolkata, India, on May 12 for medical treatment.

The detained person, who is a resident of an area in West Bengal close to the international border with Bangladesh, had met one of the prime accused in the murder case, the officer said.

Anar, who arrived in the city on May 12 for medical treatment, has been untraceable since May 13, according to a senior official from the Bangladesh Deputy High Commission in Kolkata.