The man accused of being behind a series of grenade attacks in Rangoon in April this year has been charged with murder.

Phyo Wei Aung’s wife, Htay Htay, said that the 31-year-old was being kept in solitary confinement for 23 hours a day in Rangoon’s notorious Insein prison. Nine people died and nearly 200 were injured by the bombings on 15 April, which targeted crowds celebrating the annual water festival.

“He’s being kept alone in the prison and allowed only one hour walking time,” said Htay Htay. “He wants to talk with other people and play chinlone [Burmese ball sport]. His brother is making an official request to allow him the same privileges as other inmates in the prison. This is bad for [Phyo Wei Aung's] mental health.

The engineer suffers from Hepatitis B, his wife said. He is facing four charges, under the Electronics Act, the Explosives Act, the Unlawful Associations Act and the Immigration Act, as well as the murder charge.

The Burmese government claims he is a member of the Vigorous Burmese Student Warriors, which stormed the Burmese embassy in Bangkok in 1999 and took 38 hostages.

Although he appeared healthy, albeit slightly gaunt, when Htay Htay visited earlier this week, she said that prison authorities only began passing on medicine from the family a fortnight ago. He has been held since 23 April.

Phyo Wei Aung made his first appearance at the special courtroom inside Insein prison in 30 June, where the charges were announced. “He is facing four charges…so God help him,” Htay Htay said.

Three separate grenade attacks hit the X20 pavilion in Rangoon on 15 April, as revellers celebrated the Thingyan festival. It was the most deadly attack on Rangoon in half a decade.