Police say three farmers died in Cambodia after their tractor struck an anti-tank mine left over from the country's civil war.

Deputy police chief Noun Muth of the district of Samlot says the accident took place Sunday.

Muth said Monday that three people died instantly and three others were critically wounded.

Samlot is in a former stronghold of the Khmer Rouge, who ruled Cambodia in the late 1970s and was an active rebel group through the 1990s.

An estimated 4 million to 6 million land mines and other unexploded ordnance still remain in Cambodia from more than three decades of armed conflict.

A similar explosion last week also involving a tractor in northwestern Battambang province killed six people and wounded two others.