The remains, many still fitted with rusted handcuffs and leg irons, were discovered by workers clearing the demolished market site where Hanoi authorities say they plan to build a road, the online VNExpress said.

'Am Phu' (hell) market was later formally called the '19/12 Market", to commemorate Dec 19, 1946, the start of the Vietnamese resistance against French forces reoccupying their colony after Japan's World War II occupation.

The market was built on the site of a mass grave where French forces interred the bodies of Vietnamese resistance fighters, political prisoners and war victims, said historian and legislator Duong Trung Quoc.

Hanoi authorities in the 1980s moved some bodies from the market to a cemetery, but traders continued to burn incense for the spirits of the dead.

'No one knows how many bodies were in that mass grave,' Mr Quoc told AFP. 'I guess none of them were buried properly.'

The market later became a popular tourist spot, in part because several vendors there sold dog meat, considered a delicacy in Vietnam.

Hanoi city leaders sparked protests from citizens, historians and architects late last year when they said they would bulldoze the traditional market and build a 17-storey commercial and shopping centre on the site.

The 300-odd traders were moved to another site and their market stalls torn down, but last week city authorities decided to turn the site into a road instead and build the shopping centre in a nearby street, said VNExpress. -- AFP