One of the few survivors of a notorious Khmer Rouge torture centre from which thousands of people were despatched to their deaths has revealed how he and the other inmates scrabbled to find insects to eat to avoid starvation and ate their paltry meals alongside the corpses of those who had died. At times he thought about eating the remains of the dead.

Van Nath, an artist who dodged death only because of his ability to produce a portrait of the regime's leader, Pol Pot, told a genocide trial in Cambodia that although he escaped with his life 30 years ago he was still shackled by his memories.

Wiping away tears as he launched into a series of harrowing recollections, the 63-year-old said: "My suffering cannot be erased - the memories keep haunting me."

As he gave his testimony the white-haired survivor was face to face with his jailer, Kaing Guek Eav, also known as "Comrade Duch", the head of Tuol Sleng jail where Mr Nath was held between January 1978 until January 1979.

Duch is one of five former regime members being tried by the joint UN-Cambodian inquiry.

"We were so hungry, we would eat insects that dropped from the ceiling. We would quickly grab and eat them so we could avoid being seen by the guards," said Mr Nath, who lost two children during the four years the Maoist-inspired regime controlled the country.

"We ate our meals next to dead bodies, and we didn't care because we were like animals. The conditions were so inhumane and the food was so little. I even thought eating human flesh would be a good meal."

In a country where 1.7 million people died at the hands of the Khmer Rouge either by execution, starvation or disease, Mr Nath is that rare thing: a survivor.

Of the estimated 14,000 people sent to Tuol Sleng to be tortured and interrogated before being dispatched for execution at "killing fields" on the edge of Phnom Penh, barely a dozen are known to have lived through it, and just six are still alive today.

Mr Nath said the only reason he survived was because Duch learned that he was a trained artist.

He was quickly asked to produce portraits of Pol Pot, the regime's leader who died in 1998.

"I survived because Duch felt good when he walked into my workshop," he said.

But he also revealed details of the torture suffered before Duch learned of his talents. He was beaten, electrocuted, had his fingernails pulled out, and also underwent a form of "water-boarding". Prisoners, he said, were fed six teaspoons of rice porridge a day.

Duch, who showed little reaction as he watched Mr Nath give evidence, is the first former Khmer Rouge leader accused of crimes against humanity to go on trial.