A baby and a five-year-old girl were killed in an explosion east of Vietnam's capital Hanoi today that destroyed several houses and wounded at least six other people.

Authorities are investigating the cause of the blast in Bac Ninh province's Yen Phong district, which occurred at 4:30 am demolishing buildings and sending debris flying through the air.

The explosion completely razed five homes and shattered the windows of surrounding buildings, according to an AFP reporter at the scene.

A one-year-old boy and a girl were killed, according to a report from the provincial health department seen by AFP, while six others were taken to hospital with injuries.

"The blast seemed to be in an area where there are many families involved in collecting scrap," a local official told AFP, requesting anonymity.

Salvage of metal from the tonnes of Vietnam War-era bombs that still blanket the country often ends in tragedy.

In August six people were killed, including three children, when a war-era bomb exploded in Kanh Hoa province. Reports at the time suggested it detonated as scrap workers cut it open.

Since the end of the Vietnam War in 1975, more than 42,000 people have been killed and over 62,100 injured by unexploded ordnance dropped by US aircraft, according government figures.