The three most senior surviving leaders of Cambodia's brutal Khmer Rouge regime have gone on trial.
They include Nuon Chea, also known as Brother No.2. He was the right-hand man of the Maoist regime's supreme leader Pol Pot, who died in 1998.
The former leaders, now all in their 80s, face charges including genocide and crimes against humanity.
The Khmer Rouge regime fell in 1979, and the process of trying its leaders has taken many years.
Cambodia originally asked the United Nations and international community to help set up a tribunal into the genocide in the mid-1990s, reports the BBC.
A joint tribunal was finally set up in 2006 following drawn-out negotiations between the government in Phnom Penh and the UN - but to date, only one person has been convicted.
The other leaders on trial now are the regime's former head-of-state Khieu Samphan, and Ieng Sary, who was foreign minister and international face of the organisation.
The regime attempted to create a communist society by forcing city residents to work as peasants in the countryside, and by purging intellectuals and middle class people.
About 1.7 million people - about one-third of the population - are believed to have been murdered, or died of over-work, starvation or torture from 1975 to 1979.