A former army captain turned charity worker who was arrested earlier this month by Burmese intelligence may have been tortured during interrogation, his family has told DVB.

The location of Nay Myo Zin and the reasons for his arrest on 2 April have been kept hidden from family members, who recently sent a letter of complaint to Burmese President Thein Sein.

Nine days after his arrest, police blocked an attempted visit by his parents and brother to the Aungthabyay interrogation centre in Rangoon where he was rumoured to have been taken. Little information about him has since surfaced.

“The police supervisor, U Shwe Linn, said my son was mentally weak, although he has a big body,” said Nay Myo Zin’s mother, Khin Thi. “I can’t imagine how badly they are torturing him.”

The 36-year-old had been volunteering at a Rangoon blood donation group started in 2009 by Nyi Nyi, a member of the National League for Democracy.

Groups such as these that operate outside state-run initiatives are often viewed with suspicion by the government, which has been known in the past to jail civilian relief and charity workers.

The family say they are suffering under the strain of his detention. Nay Myo Zin’s wife was undergoing “mental” difficulties, his brother, Khin Maung Htwe, said.

“Their child has also suffered a lot. As a young child, the family have had to sooteh him a lot. Now I’m taking responsibility for two families as my brother is in this situation.”

Arrested three days after Burma’s new president was sworn in, Nay Myo Zin becomes the first so-called ‘political’ detainee of Burma’s nominally civilian government.

Nay Myo Zin resigned from his army post in 2005 and has since been an active charity worker and relief worker. Khin Maung Htwe said his arrest was unlawful and called on the government to release him.

His mother earlier told DVB that he had left the army on his own volition because “he didn’t enjoy it there… He is a morally strong kid who is very devoted to charity work but [has] no involvement in politics”.

Under Burmese law, the family of a detained person has the right to know their whereabouts after 24 hours, although this is often ignored.