The most senior surviving member of the Khmer Rouge regime was arrested in Cambodia on Wednesday and charged with war crimes and crimes against humanity.

Khmer Rouge official Nuon Chea is escorted onto a helicopter near his home in Pailin, Cambodia, on Wednesday.
(Heng Sinith/Associated Press)

Nuon Chea, who is also known as Brother Number Two, will be tried in the capital city of Phnom Pehn by a UN-backed genocide tribunal made up of foreign and Cambodian judges.

Nuon Chea was arrested by police, soldiers and security guards at his jungle home in Pailin, near the Thai border.

"He was shaking, his legs looked like they would collapse," neighbour Sok Sothera told the French news agency, AFP.

Nuon Chea, 82, was second in command to Khmer Rouge leader Pol Pot, or Brother Number One.

Pol Pot, who died in 1998, founded the Maoist Khmer Rouge regime with the vision of transforming the heavily forested Cambodia into an agrarian peasant utopia. Instead, the regime, which was in power from 1975 to 1979, is blamed for the deaths of 1.7 million people.

Most died of starvation, overwork or execution. Many of the victims were killed and buried in mass graves at locations known as "killing fields."

Analysts say Nuon Chea, a Thai-trained lawyer, rose through the ranks and took on an important decision-making role in the regime, according to the BBC. He has repeatedly denied responsibility for any of the deaths but has said he's ready to face the tribunal.

His son, Nuon Say, told Reuters the officers who arrested his father took documents and photos from the home before taking Nuon Chea to Phnom Pehn  by helicopter.

"My dad seems to have no worries, but my mother is worried about him," Nuon Say said.

The tribunal's trials are expected to begin next year.

Only one other Khmer Rouge official has been arrested and is to appear before the tribunal — Kang Kek Ieu, who was also known as Duch.

Duch was in charge of the S21 jail in Phnom Penh, where more than 17,000 men, women and children are said to have been imprisoned and tortured, according to the BBC.

Duch was arrested in July, while four other people are said to be under investigation.