UNITED NATIONS (Reuters) - The prosecutor of the new International Criminal Court said he was investigating killings, mass rapes and other atrocities in lawless Darfur but had not been able to conduct inquiries in Sudan itself.

Luis Moreno Ocampo, whose report was obtained by Reuters, on Tuesday addresses the U.N. Security Council, which asked him last March to prosecute individuals responsible for atrocities in Darfur.

After identifying "particularly grave events" such as the "high numbers of killings," mass rapes and other crimes, he said he had "now selected a number of alleged criminal incidents for full investigation."

But his team of 29 experts has not been able to interview witnesses in Sudan. Instead, Moreno Ocampo, an Argentine, said he had "screened" 100 potential witnesses outside of Sudan and said he expected assistance from 11 nations and 17 advocacy and humanitarian groups.

In addition, he said his office had analyzed more than 2,500 items collected by a U.N.-established inquiry commission that reported last January.

The prosecutor, who has made one trip to Khartoum to talk to government officials, said he hoped to visit Sudan's special court and other judicial bodies investigating crimes in Darfur early next year.

Under the 1998 Rome statutes setting up the Hague-based International Criminal Court (ICC), the prosecutor can only conduct investigations when national courts are unable or unwilling to do so.

Among 160 suspects, Sudan's special court has convicted 13, including one for murder, Moreno Ocampo said.

But in an 85-page report over the weekend, timed for his visit, the New York-based Human Rights Watch said not one mid- or high level government official, military commander or militia leader had been suspended, prosecuted or investigated by Sudanese courts.

Moreno Ocampo gave a list of actions he would or could not take, including the almost impossible task of protecting witnesses. He also said he was considering whether a prosecution would interfere with the peace process.

And he said a list of 51 suspects given to him by the U.N. inquiry commission last April was "in no way binding" and had to be re-investigated by his staff.

That commission urged suspects be tried by the ICC and accused the government and allied Arab militia of torture, rape, killings and pillaging. It also accused Sudanese rebels of violence.

The United Nations has called Darfur one of the world's worst humanitarian crises, saying the conflict between the rebels, the government and its allied Arab militia has caused countless deaths, rapes and uprooted 2 million people.

The International Criminal Court is the first permanent global war crimes tribunal, first envisioned after the Nuremberg trials at the end of World War II.

It was set up to try individuals for genocide, war crimes and crimes against humanity committed after July 1, 2002.

The United States vehemently opposes the tribunal, arguing that it could initiate politically motivated prosecutions of American troops and officials abroad. But it allowed the council last March to refer Darfur to the ICC by abstaining.

A total of 100 countries have ratified the 1998 Rome Treaty that established the court and believe it contains enough safeguards to prevent frivolous prosecutions.