PHNOM PENH (REUTERS) - Hundreds of people gathered at one of Cambodia's most notorious "Killing Fields" on Thursday (May 18) to remember victims of the Khmer Rouge genocide of at least 1.8 million Cambodians in the 1970s.

Most of the victims died of starvation, torture, exhaustion or disease in labour camps or were bludgeoned to death during mass executions. At Choeung Ek, some 15km from the Cambodian capital, heavy rains to this day wash fragments of bone and scraps of the victims' clothing from mass graves.

A tower of skulls and bones stands at the centre of a memorial to an era in which hardly any Cambodian family was spared losses.

"I offer this food through the monks to those who were killed and I ask them to wish us and the country good luck and that there will be no more fighting or killing in the future,"said 59-year-old Keo Oun at the memorial.

The Khmer Rouge ruled Cambodia from 1975 to 1979.

The Day of Remembrance, once known as the "Day of Hatred", is usually held on May 20 but was brought forward this year due to local election campaigning.

Tension has been rising ahead of the election next month.

Prime Minister Hun Sen, a former Khmer Rouge cadre who has ruled for over three decades, has warned of possible civil war if his Cambodian People's Party doesn't win elections. His opponents accuse him of using intimidation and underhand tactics to keep his grip on power.