Cambodians across the country have marked the 25th anniversary of the fall of the Khmer Rouge.
Prime Minister Hun Sen took part in the commemorations
It was on this day in 1979 that Vietnam invaded Cambodia and ended the rule of the brutal regime led by Pol Pot.
But the BBC's South East Asia correspondent, Kylie Morris, says the deaths of an estimated 1.7 million Cambodians have barely been acknowledged by those responsible.
After years of impunity, now the government says justice is imminent.
In a speech to mark the anniversary, the president of the ruling party, Chea Sim, said those who suffered must receive justice.
He said this would be done via a tribunal set up to prosecute those responsible for their crimes.
"We will always remember the most horrific events of three years, eight months and 20 days under the regime of Democratic Kampuchea, which carried out the most cruel genocide policy resulting in massive and limitless destruction.
"We will be able to completely close down this dark chapter through the successful implementation of the law to form an extraordinary tribunal to judge the crimes committed under the Democratic Kampuchea regime," he said.
His speech, which was broadcast on national television, was concluded with children releasing doves and balloons to symbolise peace.
Six former leaders of the Khmer Rouge are due to face the tribunal, sponsored by the United Nations, which is expected to begin its work in the coming months.
But a political deadlock in the country following elections in July has led to delays, despite agreement between the government and the UN nearly a year ago.
The defendants will include the former Khmer Rouge president, Khieu Samphan, who admitted recently that mass killings did in fact take place between 1975 and 1979.
The former party leader currently raises ducks on a farm close to the Thai border.
He says he only found out about the genocide when he watched a documentary film recently about a torture centre where thousands were held before being taken to their deaths in the so-called "killing fields".
He denied personal responsibility for any killing and says that much of what happened in Cambodia in those years was as a result of the Cold War.
But Brother Number One - Pol Pot - is one who will never be called to account - he died five years ago, although not before stating that his conscience was clear.
Our correspondent says such easy truths remain beyond the reach of his fellow Cambodians, still struggling to be free of his regime's terrible legacy.