As the Khmer Rouge tribunal continues to hear evidence on internal killings and alleged rebellions, witness Norng Nim yesterday testified that it was Brother Number One Pol Pot who launched a “coup d’état” against his own soldiers in a series of brutal purges.

Nim, 65, who was a distant relative and former driver for East Zone secretary Sao Phim, testified via audio-visual link from Tbong Khmum province in the case against surviving Khmer Rouge senior leaders Nuon Chea and Khieu Samphan.

While Phim committed suicide in June 1978 after being surrounded by Khmer Rouge central forces – who believed he and Northwest Zone secretary Ruos Nhim were planning to overthrow Pol Pot – Nim said it was Pol Pot who had launched a “coup” by arresting East Zone cadre.

“It means Pol Pot arrested soldiers to be killed,” Nim told judge Claudia Fenz, who had asked him what he meant by “coup d’état”. The alliance between Nhim and Phim – cemented by the marriage of their children – and their alleged plans to undermine Pol Pot are key elements in Chea’s defence.

The pair would, in jest, refer to each other as Ah Siam, “contemptible Thai”, and Ah Youn, “contemptible Vietnamese”, as they shook hands and hugged each other, Nim said. “They rarely saw each other, and when they met each other they were jokingly teasing each other . . . I did not know the meaning behind the words they used.”

Nim said in the two weeks leading up to Phim’s death, there had been several arrests and killings of East Zone senior cadre, and only in the “last wave” of arrests did Phim realise he was next. Phim went to meet with Pol Pot in Phnom Penh to find out about the arrests – a trip that proved to be his last.

“He was an honest person, he chose to stay and face the truth,” he said. Nim confirmed a force of 300 people assembled after Phim’s death to fight Pol Pot. “We created that force in order to defend our people and prevent the killings,” he said.

When Nim said he had forgotten many key details he provided in a statement last year, Chea’s defence lawyer Victor Koppe questioned whether Nim’s memory was really at fault. “Are you afraid to speak in public, or is there something else going on?” Koppe said.

The witness maintained he was merely forgetful. A second witness, identified as 2-TCW-823, testified that he received orders from Khieu Samphan to evacuate workers – who they feared might rebel – in the event of a Vietnamese invasion.