Three officials and five visitors died at Yangon's colonial-era Insein prison after two explosions went off at 9.40am on Wednesday local time near the facility's parcels counter, according to independent news portal Myanmar Now.

It was unclear what caused the explosions.

Police were at the scene and inspecting the site of the explosions shortly afterwards, media reported.

Prison staff and couriers who were seriously injured were evacuated from the prison, while those not seriously injured were treated at nearby shops, according to BBC Burmese.

A number of cases scheduled to be heard in the adjacent court, were cancelled after the explosions, according to media reports.

A spokesperson for the military government did not answer phone calls requesting information. Insein is the country's most notorious prison and thousands of political prisoners have been sent to the facility since last year's military coup.

Australian Associated Press