File photo - A defused mortar head is planted during a mine and unexploded ordnances awareness class for school boys in Qarabagh district.

Phnom Penh, Cambodia -

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 on 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 eight and the other nine years old.

They were killed on 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 - Sapa-AP