A top Khmer Rouge leader blamed "unruly elements" within the Khmer Rouge's brutal Maoist regime in the late 1970s for the estimated 1.7 million civilian deaths.

Nuon Chea, standing trial for genocide, told a U.N.-backed court in Cambodia, that he had nothing to do with the deaths, a report by the BBC said. He also denied involvement in torture, saying he was serving the nation to protect it from foreigners.

"My position in the revolution was to serve the interests of the nation and people," he said during his 90-minute speech in the court.

"I had to leave my family behind to liberate my motherland from colonialism and aggression and oppression by the thieves who wished to steal our land and wipe Cambodia off the face of the Earth."

His remarks opened the trial eagerly awaited by millions of Cambodians, who as young and middle-aged people fled the regime.

Nuon, as deputy leader to Pol Pot, was known as Brother Number Two and oversaw the Year-Zero plan, a mass migration of people from cities to work as peasants on communal farms in the countryside.

The policy included the abolition of money and private property, as well as banning religion in the country they called Democratic Kampuchea.

The result was the starvation and death by disease of an estimated several million people in what became known as the Killing Fields. Thousands more were jailed in Phnom Penh's Tuol Sleng Prison, called S21 and known for brutal torture.

In the end, it was an invading Vietnamese army that overthrew the regime whose leaders and cadres, including Pol Pot, fled into the jungle where they remained for years.

Lead prosecutor Andrew Cayley said Nuon, along with Khieu Samphan, the Maoist regime's former head of state, and Ieng Sary, its former foreign minister -- all in their 80s -- are accused of systematically organized crimes of genocide during the four-year regime.

"These crimes were the result of an organized plan developed by the accused and other leaders and systematically implemented" by the Khmer Rouge command, he said. "They can't be blamed solely on Pol Pot as some of the accused may try."

The regime's most wanted man was Pol Pot. He was captured in 1997 and under house arrest when he died in 1998. Although not proved, it's been suggested that he either was poisoned or committed suicide.

The tribunal was set up in 2006 but it wasn't until 2010 that it sat for the first time. In July 2010 it handed down a 35-year jail sentence to S21 Khmer Rouge prison boss Kaing Guek Eav, 67 and also known as Duch.

The five-judge panel later reduced his sentence to 19 years. He admitted to overseeing the torture and deaths of around 14,000 people -- including children -- at the prison.

The current case will continue without a fourth defendant, that of Ieng Thirith, wife of Ieng Sary and minister for Social Affairs in the regime. The judges ruled last week that she was suffering with what appeared to be Alzheimer's disease and the charges against her would be stayed.

The trail continues and watched by some Cambodians living abroad but who traveled to Phnom Penh to see justice done.

"The victims, especially myself, we suffer for too long," said Marie Chea, 60. "Why wait too long, until now? Why don't they do anything? What is the truth? We want to know the truth."

The Ashburn, Va., resident is one of three Cambodian-Americans who returned to the country to watch the trial.

They were taken to Cambodia as part of a program by the Applied Social Research Institute of Cambodia, a non-profit group based in New York that registered 41 Cambodian-Americans as civil parties to the trial, with the right to demand symbolic reparations.