THE HAGUE, Netherlands - Seif al-Islam Gadhafi will eventually face justice in The Hague but it's not clear where the son of Libya's former dictator is hiding, the prosecutor of the International Criminal Court said Wednesday.

Luis Moreno-Ocampo also said he was making headway with an investigation into allegations of widespread rapes by Gadhafi supporters.

Asked if he believed the rapes were part of an organized campaign of sexual abuse, Moreno-Ocampo told The Associated Press, "I think so. We have one witness who was a soldier who says he received instructions to rape."

Investigators are now trying to pin down exactly who ordered the sex attacks. "We are trying to connect the rapes with instructions given by commanders," he said.

Moreno-Ocampo told the UN Security Council last week that investigators are probing hundreds of alleged rapes, but he said the true number could run to thousands. He said it is difficult to establish the exact number because victims are reluctant to report rapes.

Meanwhile, the court's investigators are "following information about the probable whereabouts" of Seif al-Islam and former Libyan intelligence chief Abdullah al-Senoussi "and we are encouraging efforts to arrest them."

The two were indicted by the International Criminal Court in June for unleashing a campaign of murder and torture to suppress the uprising against the Gadhafi regime that broke out in February. Gadhafi himself also was indicted, but the case against him will be dropped after he died at the hands of rebels who captured him last month outside his hometown of Sirte.

Unlike his father, Seif al-Islam is believed to have slipped out of the country and his whereabouts are unknown.

Seif al-Islam and al-Senoussi were thought to have fled to Mali. The government there has said it will arrest them if they are caught.

Moreno-Ocampo has said the court is pressing countries to prevent Seif al-Islam's escape by denying any plane carrying him permission to fly through their air space. He mentioned Zimbabwe as a possible country where the fugitive could seek refuge.

Moreno-Ocampo said late last month he was in indirect contact through an intermediary with Seif al-Islam about the possibility of Gadhafi's son turning himself in. But the contacts appear to have led nowhere.

Even so, Moreno-Ocampo said Wednesday "it is a matter of time" before Seif al-Islam is arrested and brought to justice.

"It is not if he will be arrested, it is when," Moreno-Ocampo said. "Seif will face justice, that's his destiny."

Seif al-Islam, whom the court described as the de facto prime minister during the early months of the uprising, was the heir apparent in the regime that ruled Libya for 42 years.

The UN Security Council authorized the court, the world's first permanent war crimes tribunal, to investigate events in Libya in February.