PHNOM PENH - Cambodia held ceremonies across the country on Sunday to celebrate UNESCO's recognition of three former Khmer Rouge sites as World Heritage, honouring their transformation from centres of repression to places of peace and reflection.

The Tuol Sleng prison and Choeung Ek killing fields in Phnom Penh, and M-13 prison in Kampong Chhnang province were inscribed as "Cambodian Memorial Sites: From centres of repression to places of peace and reflection" during a UNESCO meeting in Paris on Friday.

"This is a model for the world, showing the long struggle of Cambodia, reconciliation, the spirit of national unity, finding justice for the victims and building peace," said interim Culture Minister Hab Touch.

The Khmer Rouge sites mark Cambodia's fifth World Heritage listing, and is the country's first modern-era nomination and among the first globally tied to recent conflict.

The sites are a stark reminder of the atrocities committed under Pol Pot’s regime from 1975 to 1979, during which an estimated 1.7 million to 2.2 million people died, many from starvation, torture, or execution.

The Tuol Sleng prison, which held approximately 15,000 prisoners, is now a genocide museum. REUTERS