The blasts hit a crowd lining up to drop off parcels for inmates at Insein Prison on Wednesday morning, the junta's information team said in a statement, without specifying exactly how many explosions had occurred.

The junta said "terrorists" were responsible.

Local media, citing prison officials, said at least three prison staff were among the dead.

Pictures in local media purporting to capture the aftermath showed what appeared to be bloodstains on the floor around a counter, and shattered windows behind.

According to a witness, security forces locked down the area around the sprawling, colonial-era prison, which rights groups say holds hundreds of prisoners detained by the junta in its crackdown on dissent.

The Southeast Asian country has been in turmoil since the military seized power in a coup last year.

Self-declared civilian "people's defence forces" have sprung up across the country to fight the junta.