The Khmer Rouge's former jailer said on Tuesday the regime practised a "criminal" mix of the theories of Marx, Lenin and China's "Gang of Four" as it killed thousands of people in the 1970s.
Kaing Guek Eav, better known by his name De Guerre Duch, is on trial for overseeing the torture and extermination of 15,000 people who passed through the hardline communist movement's notorious Tuol Sleng prison.
Duch told the UN-backed war crimes court that Khmer Rouge leader Pol Pot, who died in 1998, applied a mix of communist ideas to orchestrate extreme social reforms.
But he said that the regime had "more seriously cruel policies than those of (the) Gang of Four of China" since it enslaved the population on collective farms and began to carry out mass killings immediately after seizing power.
"The policy of (the Khmer Rouge) was criminal," Duch said. "The killing was widespread."
He added that only the "collective peasant class and collective worker class" remained throughout the country after the educated and elites were murdered.
The former 66 year old maths teacher wearing a white long-sleeved shirt, told the court that the Khmer Rouge's policy was to root out all enemies who did not share its ideology.
Duch apologised at his trial in late March, saying that he accepted blame for the extermination of thousands of people at the prison, which served as the centre of the 1975-1979 regime's security apparatus.
On Monday Duch told the trial that his staff had murdered babies by smashing them against trees at a "killing field".
But he has denied prosecutors' claims that he played a central role in the Khmer Rouge's iron-fisted rule, and maintains he only tortured two people himself and never personally executed anyone.
Duch faces life in jail if convicted by the court. Many believe the tribunal is the last chance to find justice for victims of the regime, which killed up to two million people.
The court was formed in 2006 after nearly a decade of wrangling between the United Nations and the Cambodian government, and is expected next year to begin the trial of four other senior Khmer Rouge leaders also in detention.