1.7 million people are believed to have died in the "Killing Fields"

Cambodian Muslims attend a ceremony to mark the 29th anniversary of the toppling of Pol Pot's Khmer Rouge regime in Phnom Penh January 7, 2008 . Some 1.7 million people are believed to have died in the "Killing Fields" of the ultra-Maoist guerrillas, whose four year reign of terror was brought to an end in 1979 by invading troops from neighbouring Vietnam