NIAMEY, Niger — Moammar Gadhafi's playboy son, known for his love of fast cars, soccer and excessive partying, slipped into Niger over the weekend and began making his way to the capital, a Niger government official said.

In Washington, State Department spokeswoman Victoria Nuland confirmed Monday that al-Saadi Gadhafi has crossed into Niger, where authorities "are either in the process or have already brought him to the capital of Niamey and intend to detain him."

The 38-year-old al-Saadi Gadhafi is one of the highest-profile former regime figures to flee to this landlocked African nation whose immense northern desert has been a haven for drug smugglers, al-Qaida terrorists and now fleeing Libyan loyalists. The discovery is bound to raise pressure on Niger which has promised to turn over anyone wanted by the International Criminal Court which includes Gadhafi and a different son.

The country, however, has not said whether they will turn over other regime figures, like al-Saadi, who are wanted by Libya's new interim government but are not the subject of a warrant by the world court.

Nuland said that although al-Saadi wasn't on a U.N. sanctions list, the government of Niger has made it clear to Libya's de facto government that it will cooperate on cases of fleeing regime loyalists.

"We are encouraging dialogue between them," Nuland said, adding that Libya's opposition leaders would make their own decision about the appropriate course of action.

By late Monday, the ex-ruler's son had made it only as far as Agadez, a town 370 miles (600 kilometers) south of the Libyan border which is still over 500 miles (900 kilometers) from the capital. He was being housed in the governor's mansion, said an official with the Agadez City Council who asked not to be named because he's not authorized to speak to the press.

Agadez is where earlier convoys carrying Gadhafi's senior officers including several generals had stopped. Three of the generals had been summoned to the capital and were en route to the city Monday, said one of Gadhafi's commandos Agaly Alambo, an ethnic Tuareg from Niger who crossed into Libya to fight for Gadhafi.

"They need to talk and finish business with the authorities here, so that everyone is on the same page," Alambo told The Associated Press by telephone. "They are seeking refuge." A four-car convoy of Toyota Land Cruisers was seen speeding into town after night had fallen, lights blinking late Monday, but it was not immediately possible to confirm if the cars filled with turbaned men was carrying the Libyans.

Niger appears to have become the only exit for members of Gadhafi's inner circle. After the ruler's wife and several of his other children crossed into Algeria, that border was sealed. It's unlikely they would flee east to Egypt because they would need to go through rebel-held territory. And the Chadian frontier has proved difficult to cross.

Niger's border with Libya is vast and impossible for the country's ill-equipped and cash-strapped army to monitor. Since last week, waves of convoys carrying regime officials have drifted across the invisible line set on undulating dunes. They include other top regime figures like Gadhafi's chief of security and the general in charge of the country's southern command.

The arrival of al-Saadi takes it to a new level of intimacy, indicating that even the ruler's family is choosing Niger as their best option.

"Nobody called us to tell us that these people were coming," government spokesman Morou Amadou told The Associated Press by telephone on Monday. "We intercept them as they are making their way south and they run into our patrols. We are allowing them to enter on humanitarian grounds since we cannot send them back to a war zone."

The arrival of the son also raised speculation that Gadhafi may eventually be headed to Niger. "There are strong suggestions that he is going to be convoyed here," said an immigration official who asked not to be named because he was not authorized to speak to the press.

"First, there is our proximity. We are closest to the areas of Libya that are still under Gadhafi's control. But beyond proximity, there is the fact that the Algerian side is now shut," the official said. "They can't go to Egypt because of the rebels. Chad is also closed. That leaves only one place — Niger."

Last week, the U.S. urged Niger to detain any individuals who may be subject to prosecution in Libya, and to confiscate their weapons and impound any state property, such as money or jewels, that were illegally taken out of the country. Amadou said that al-Saadi, who was traveling in a nine-person convoy, was asked to hand over his weapons.

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There have been unconfirmed reports that Gadhafi regime members are fleeing with cash and gold looted from the nation's banks. Amadou said he does not know what the son was carrying in terms of valuables, but his lifestyle in Libya before his father's fall was marked by luxury.

When rebels rode into Tripoli last month, they stormed al-Saadi's home on the Mediterranean. In the parking lot they found a white Lamborghini. The son, a soccer aficionado was described in a 2009 WikiLeaks cable from the U.S. Embassy in Tripoli as having a troubled past, including run-ins with police in Europe, drug and alcohol abuse and excessive partying.

In an office area in the villa, reporters saw large piles of catalogues for yachts and cars. A catalog by the firm Benetti had a yellow handwritten post-it note attached listing the price for a 30-meter-long yacht as 7 million euros.

Associated Press Writers Dalatou Mamane in Niamey, Niger, Hadeel Al-Shalchi in Wadi Dinar, Libya, Maggie Michael in Cairo, and Ben Hubbard and Ryan Lucas in Tripoli, Libya, and Bradley Klapper in Washington contributed to this report.