A land mine killed five Cambodian soldiers and maimed another as they tried to remove it from an area being developed to build a casino, an official said Wednesday.

The surviving soldier lost a leg in the powerful blast Tuesday, said Pech Sokhen, governor of the northwestern province of Oddar Meanchey, where the explosion occurred.

"They had been hired by the land owner to clear mines for building a hotel and casino resort," he said. It was not clear if the explosion was caused by more than one mine.

Oddar Meanchey, near the Thai border, remains littered with land mines.

An estimated 4 million to 6 million mines and other unexploded ordnance remain buried in Cambodia from more than three decades of armed conflict. Explosions maim or kill many Cambodians each year.

Last month, 10 rice field workers were killed when their truck drove over an anti-tank mine in Oddar Meanchey, 200 miles northwest of the capital, Phnom Penh. A similar accident left 13 villagers dead in November.