UNITED NATIONS — The United Nations on Tuesday strongly denied that it had ordered Cambodia war crimes judges to reject a new case involving the Khmer Rouge.

With the country gearing up for a major Khmer Rouge era trial this month, Cambodian media reports said five UN staff have resigned in protest at a decision to close the new case without properly investigating the charges.

The UN-backed war crimes court has threatened legal action in a bid to prevent publication of leaked details of the case.

"The United Nations categorically rejects media speculation that we have instructed the co-investigating judges to dismiss Case Three," said UN spokesman Martin Nesirky of the new Khmer Rouge inquiry.

The names of the suspects in the case have not been made public, but they are thought to be two ex-commanders from the brutal 1975-79 Khmer Rouge regime blamed for up to two million deaths.

"Support for the independence of the judiciary is a fundamental principle that the United Nations upholds in Cambodia as elsewhere," said Nesirky.

Judges and prosecutors at the Cambodia courts "must be allowed to function free from external interference by the royal government of Cambodia, the United Nations, donor states, and civil society," he added.

The Cambodia war crimes court's second trial starts on June 27. Among the four defendants are Khieu Samphan, the former Khmer Rouge head of state, and Nuon Chea, the deputy to notorious regime leader Pol Pot.

Prime Minister Hun Sen has repeatedly voiced his objection to further trials, however, saying they could plunge the country into civil war.

The international court's investigating judges have been under fire ever since they announced in April they had concluded their investigations into case three, without questioning the suspects.

International co-prosecutor Andrew Cayley -- without the backing of his Cambodian colleague -- demanded the suspects be interviewed and more crime scenes examined but the judges rejected his request last week on technicalities.

Nesirky said the UN will "not comment on issues which remain the subject of judicial consideration, nor speculate on actions that should or should not be taken by the judges or prosecutors in any case."

He added however that the investigating judges "are not under an obligation to provide reasons for their actions at this stage of the investigation in Case Three."

Nesirky said the trial starting this month "will be of true international significance and deserves the ongoing, strong support of the international community."