Three Cambodian boys have been killed by a B-40 rocket left over from the country's 1980s civil war.

District police chief Keo Tann said Monday the boys found the rocket in a northern forest and tried to smash it apart, hoping to sell its pieces as scrap metal.

Two of the boys were 8 and the other 9.

They were killed Sunday in Oddor Meanchey province, a site of intense battles between the former Khmer Rouge regime and government forces.

An estimated 4 to 6 million land mines and other unexploded ordnance from more than three decades of armed conflict continue to maim or kill Cambodians each year