The family of a separatist leader from India's Manipur state, who was arrested earlier this month, has urged the government to disclose his whereabouts.
Rajkumar Meghen, who leads the United National Liberation Front (UNLF), was held by Bangladeshi police and handed over to Indian authorities.
His son told the BBC that the family knew nothing about his whereabouts and was "very worried" for his safety.
The UNLF is the oldest separatist group in India's north-east.
Formed in 1964 to fight for Manipur's liberation from India, the group is estimated to have 5,000 armed fighters. It is the only group which has managed to retain territory in some areas of Manipur's borders with Burma, despite repeated military offensives by the Indian army.
Mr Meghen, whose alias is Sanayaima, was flown out of Bangladesh recently in an Indian aircraft, senior Indian officials told the BBC earlier this month.
Indian authorities have not commented publicly on Mr Meghen's whereabouts.
His mother and wife have also appealed to the United Nations High Commissioner for Refugees for help in obtaining details about Mr Meghen.
"I have no objection to the trial he may face in India or Bangladesh but we need to know whether he is alive, healthy and whether he will have access to legal aid to defend himself," his wife Rajkumari Ibenmungshi said.
A UNLF spokesman said Mr Meghen was taken to Delhi after his arrest in Dhaka and kept in the custody of India's external intelligence unit, Research and Analysis Wing (RAW).
A senior Indian military intelligence official confirmed to the BBC that Mr Meghen was in Delhi.
Bangladesh has handed over more than 50 leaders and activists of Indian separatist groups since a crackdown began in 2009. Many more have fled Bangladesh to evade capture or been caught on the border by Indian guards.