The bombs hit a crowd queuing to drop off parcels for inmates at Insein Prison, an information team for the country's junta authorities said in a statement, without specifying exactly how many explosions had occurred.

The junta blamed "terrorists" and said the dead included three prison staff and a 10-year-old girl.

It added that security forces had defused another "homemade mine" device found nearby.

One witness queuing at the counter told AFP the first blast had hit around 9:30 am local time (0300 GMT).

"Then another two went off quickly. After that we heard shooting as well," said the witness, who requested anonymity.

"I saw some people bleeding. The glass around the counter was all shattered."

According to another witness, security forces locked down the area around the sprawling, colonial-era prison after the blasts.

Rights groups say hundreds of political prisoners are held in Insein Prison, including former British ambassador to Myanmar Vicky Bowman and Japanese journalist Toru Kubota.

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

No group has claimed the attack.

A junta spokesman did not respond to a request for comment.

- Turmoil -

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 to fight the junta and have surprised the military with their effectiveness, some analysts say.

Across the country, there are almost daily killings of low-level junta officials or alleged informers, with details murky and reprisals from the military often following quickly.

Most of the violence has occurred in rural areas, although anti-coup fighters have also targeted officials and infrastructure in towns and cities.

In July a bomb blast near a shopping mall in Yangon killed two people and wounded 11.

More than 2,300 people have been killed in the military's crackdown on dissent since the coup and over 15,000 arrested, according to a local monitoring group.

The junta blames anti-coup fighters for the deaths of almost 3,900 civilians.