Survivors have marked 40 years to the day since the Khmer Rouge marched on Phnom Penh, ending a civil war but heralding an era that would kill a quarter of Cambodians and leave the capital a ghost town.

A few hundred people, including monks and elderly regime survivors, gathered early on Friday at Choeung Ek – the most notorious of the regime’s Killing Fields – on the capital’s outskirts, burning incense and chanting Buddhist prayers at a memorial stupa housing the skulls and bones of victims.

The event commemorated the April 17, 1975, triumph of the Khmer Rouge over the US-backed republican army of Lon Nol and, with it, the start of four years of a genocidal communist revolution.

Initially, the Khmer Rouge were given a cautious welcome by Phnom Penh’s war-weary residents as they entered the city astride tanks, their distinctive red-chequered scarves fluttering behind them.

But soon enough cadres began to evacuate the city of two million people at gunpoint, in one of the largest forced migrations in recent history.

The sick, elderly and very young perished, their bodies littering the roadsides, as “bourgeois” city dwellers were marched into the countryside to scratch a living from the parched soil.

By the time the tyrannical rule of Pol Pot – or Brother Number One – was toppled four years later, an estimated two million Cambodians had been killed by execution, starvation or overwork as the Khmer Rouge drove the country back to Year Zero through an agrarian peasant revolution.

“Forty years ago Pol Pot turned Cambodia into a hell – a ghost land,” Huot Huorn, 67, told AFP news agency with tears in her eyes after lighting incense for the 36 relatives she lost to the regime.

“I still hate that regime … their sins are vivid in my eyes now. They starved us, jailed people with no food and water until they died … I saw them smash children’s heads against a tree trunk.” Al Jazeera