Libya has demanded that Niger extradite Muammar Gaddafi's son Saadi, warning that his call for Libyans to prepare for a coming uprising threatened ties between the two countries, Libyan News Agency LANA said on Saturday.

As Libyan rebels gained the upper hand over Gaddafi's regime last September, Saadi and a group of senior loyalists fled across the border to Niger, where they remain under house surveillance in the capital Niamey.

In a telephone call to Al Arabiya television late on Friday, Saadi said that he was in regular contact with people in Libya who were unhappy with the authorities put in place after the ousting and killing of his father.

LANA cited a telephone call between Niger's Foreign Minister Bazoum Mohamed and his Libyan counterpart Ashour Bin Hayal on Saturday, quoting the Libyan minister as expressing strong resentment towards Saadi's aggressive statements.

Mr Ashour Bin Hayal reiterated to the foreign minister of Niger that these statements threaten the bilateral relationship between the two countries and that the government of Niger should adopt strict measures against him (Saadi) including extraditing him to Libya to be prosecuted for the crimes he committed against the Libyan people, LANA said.

Niger has said Saadi would remain in the West African nation until a United Nations travel ban on him was lifted, despite Tripoli's request for his return.

Interpol last year issued a red notice requesting member states to arrest Saadi with a view to extradition if they find him on their territory.

The foreign minister of Niger ... expressed his regret and apologies to the government and Libyan people for what has happened and confirmed that he will contact the Niger president who is on a foreign visit to France, LANA said.

He wants to assure the Libyan side that the demands made forth will be responded to in accordance to the laws and approved customs. He added that the communication between the parties will be open in this regard, LANA added.

Libyan government officials were not immediately available for comment.

BAD FOR THE NEIGHBOURS

In an interview broadcast by France 24 on Saturday but recorded before Saadi's interview was aired, Niger President Mahamadou Issoufou stated that Niger had not received any formal extradition request from Tripoli but would study any future one.

If we receive an official request we will study it. We are a state based on the rule of law. We will study that question according to our laws and our international commitments, because Niger signed the treaty that created the International Criminal Court, Issoufou told France 24.

We took them in on humanitarian grounds ... and we were very clear with them at the time: we took them in on condition they do not carry out any subversive activities against the Libyan authorities.

The ICC in the Hague issued a warrant for Gaddafi's son Saif al-Islam - who is in a Libyan jail awaiting trial on rape and murder charges - but not for Saadi, who before the war was chiefly known abroad for his obsession with soccer.

The Libyan conflict has created new problems for the fragile region to its south. Heavily armed former fighters from Gaddafi's army have joined a new rebellion in northern Mali that has forced tens of thousands to flee from their homes.

As many as 200,000 migrant workers once employed in Libya have headed back into Niger, which along with the rest of the Sahel region is facing the latest of its recurrent food crises.

Aid agencies say their arrival has stretched scarce food resources even more thinly.

(Additional reporting by Mark John in Dakar; Writing by Marie-Louise Gumuchian, Editing by Rosalind Russell)