Niger is preparing to detain al-Saadi Qaddafi, son of former Libyan strongman Muammar Qaddafi, the U.S. said Monday.

"We have confirmed with the government of Niger that al-Saadi crossed over, that they are either in the process or have already brought him to the capital of Niamey and intend to detain him," State Department spokeswoman Victoria Nuland was quoted by AFP as having said.

Nuland confirmed that al-Saadi Qaddafi was not on the list of wanted individuals under UN Resolution 1970, which imposed sanctions and travel bans on several officials in the Qaddafi regime, but urged Niger to cooperate with Libya's National Transitional Council on Qaddafi loyalists crossing over to neighboring countries.

Nuland was quoted as saying Niger "has made clear … that it is prepared to cooperate. We are encouraging dialogue between them."

On Sunday, Niger's Justice Minister Amadou Morou confirmed that al-Saadi entered Niger in a convoy with nine other people. He said the vehicles were traveling south toward the outpost of Agadez, where other fleeing Libyan loyalists are believed to be holed up in a hotel.

Qaddafi's son crossed into Niger after a large convoy of 200-250 Libyan armored vehicles had crossed into Niger the week before, giving rise to speculations that a counter insurgency was being planned.

The convoy reportedly included officers from Libya's southern army battalions and pro-Qaddafi Tuareg [Berber nomad, ed.] fighters, and is thought to have crossed from Libya into Algeria before entering Niger.

Meanwhile, Niger's Prime Minister Brigi Rafini said Monday that al-Saadi Qaddafi was among 32 members of the fugitive former Libyan leader's inner circle who have arrived in Niger since September 2.

He added that the Libyans had crossed the border in four separate groups over the last 10 days and had been taken in by Niger for humanitarian reasons. He emphasized that none of those known to have crossed over the border were being sought by the Hague-based war crimes court.

Meanwhile, back in Libya, forces loyal to Muammar Qaddafi killed at least 15 guards and injured two others in a raid on an oil facility outside the coastal town of Ras Lanuf, which is located approximately 600km east of the capital, Tripoli.  (For analysis, click here)