The Khmer Rouge carried out its policies for the sake of the Cambodian people and to protect the country from invaders, the notorious regime's second-highest leader said Tuesday at a tribunal in Phnom Penh considering charges of crimes against humanity against three top leaders.

Nuon Chea told the UN-backed tribunal it was failing to consider the complete story behind the Khmer Rouge, who are accused of being responsible for the deaths of 1.7 million people when they held power in 1975-79.

He blamed neighboring Vietnam for much of the trouble that befell his country — the same belief held by the Khmer Rouge three decades ago, as its experiment in utopian socialism fell apart.

Nuon Chea, chief ideologist for the communist movement and its No. 2 behind Pol Pot, and two former comrades — 80-year-old Khieu Samphan, the ex-head of state; and 86-year-old Ieng Sary, the former foreign minister — all avow their innocence.

Pol Pot died in 1998

The charges against these surviving members of the once-mighty inner circle of the communist movement include crimes against humanity, genocide, religious persecution, homicide and torture.

Cambodia's former President Khieu Samphan attends his trial at the Extraordinary Chambers in the Courts of Cambodia (ECCC) on the outskirts of Phnom Penh Tuesday. Mark Peters/ECCC/Handout/ReutersThe prosecution earlier Tuesday told the court Pol Pot's close confederates cannot blame their late leader alone for the atrocities that took place. Pol Pot died in 1998 in the jungle while a prisoner of his own comrades.

Prosecutor Andrew Cayley said that like Pol Pot, the three aging former members of the regime now on trial exercised life-and-death authority over Cambodia while in power in 1975-79.

"The accused cannot credibly claim they did not know and had no control over the crimes that occurred" when the group ruled what they called Democratic Kampuchea, he said.

In opening statements delivered Monday and early Tuesday, the prosecutors described a litany of horrors, recalling how the Khmer Rouge sought to crush not just all its enemies, but seemingly the human spirit.

Killing fields

Most of the population were forced to work on giant rural communes and deprived of any sort of private life. Forced marriages took the place of love, and dissenters were dispatched to the so-called "killing fields."

Nuon Chea, who spoke in time allotted for defence rebuttals of the prosecutors' statements, did little to directly address the allegations of atrocities.

He instead gave a political history of the Khmer Rouge and Cambodia, insisting that his role was always a patriotic one.

"I had to leave my family behind to liberate my motherland from colonialism and aggression and oppression by the thieves who wish to steal our land and whip Cambodia off the face of the earth," he said.

He accused Vietnam of repeatedly seeking to occupy Cambodia, a charge familiar from when the fraternal socialist neighbors first fell out in the 1970s.