The tragedy occurred at around 6:30 p.m. Monday in Nanshan Village of Haiyuan County, when villagers Yang Wanfang and Yang Zhongfa, both 28 years old, were trying to dismantle a column-shaped rusted iron bomb in their kitchen.

The bomb, 70 centimeters long and 15 meters in diameter, exploded, collapsing the wood-and-earth kitchen, killing the two men and three boys beside them and burying two girls. The girls were later rescued with only slight injuries.

One of the ill-fated boys is Yang Zhongfa's son and the other two are neighbors' children. The boys were aged 6, 13 and 15.

Windows of a nearby house were shattered and fragments of the bomb have left several holes in a brick wall.

The Yangs brought the bomb back from Inner Mongolia where they worked and hoped to sell it as scrap metal.

Police are investigating but it is not yet known when the bomb was made and what type it was.