New York - Tuesday called for Cambodia's courts to deliver a verdict on the mass killings in the 1970s by the country's Khmer Rouge government, whose leader Pol Pot died 10 years ago.

Pol Pot led communist troops to topple the US-backed government in Phnom Penh in April, 1975, and launched a country-wide sweep to wipe pout the middle class and intellectuals, resulting in more than 2 million deaths from forced labour and extermination.

He died 10 years ago this week. But Cambodia's efforts to bring the handful of Khmer Rouge survivors to justice have dragged on despite international assistance to establish a tribunal to prosecute those responsible for the genocide.

Ban called for closure on the Khmer Rouge cases, which he called "one of history's darkest chapters."

"The UN and the Royal government of Cambodia remain actively engaged in efforts to hold the Khmer Rouge senior leaders and those most responsible accountable for their horrible crimes," Ban said in a statement.

"With the support of the international community, it is my hope that the Extraordinary Chambers in the Courts of Cambodia will soon deliver long-overdue justice for the people of Cambodia," he said.