UNITED NATIONS (AP) — The U.N. secretary-general called Wednesday on the Security Council to sanction extremists who have taken over northern Mali, and he warned of worsening security and humanitarian crises in the African country.

Ban Ki-Moon asked the council to consider financial and travel sanctions on rebels and Islamist fighters, including several allied with al-Qaida. Since June, Islamists have taken over Mali's largely desert north and imposed Shariah law, recently stoning an adulterous couple to death.

The U.N. says more than 250,000 people have fled the country and 174,000 have been internally displaced since a military coup in March.

"Since the start of the crisis earlier this year, we have seen the situation take one alarming turn after another, reaching seemingly new depths with every passing week," Ban said. "These grave developments have brought enormous suffering to the people of Mali. They also pose a widening threat to international peace and security."

A 3,000-member military intervention force assembled by the Economic Community of West African States is awaiting a formal request for intervention from Mali's interim president, who recently returned from exile, an ECOWAS official said Wednesday. Dioncounda Traore will submit the request once he forms a transitional government, said Salamatu Hussaini Suleiman of Nigeria, the group's political affairs commissioner.

Traore left Mali on May 21 for medical treatment in Paris after being beaten until he lost consciousness by a mob of protesters allied with the coup leader. He returned two months later, a long absence seen as a sign that he did not trust the military to guarantee his safety.

Resistance by Mali's military has hindered the deployment of the ECOWAS force. Last month, in the first indication that the coup leaders would accept foreign troops, the military publicly welcomed a force that could provide security assistance and help regain the troubled north.

ECOWAS wants a U.N. mandate for the force, but a request from Mali will be enough to make it legal, France's U.N. Ambassador Gerard Araud said Wednesday. He said the council won't authorize the force until it gets more details.

The force has been criticized by the International Crisis Group, which issued a report last month warning against military intervention.

"ECOWAS countries willing to send troops do not appear to fully grasp the complex social situation in northern Mali, and underestimate the high risk of inter-tribal settling of scores that would result from external military intervention," the report by the nongovernmental organization said.

The crisis in Mali has escalated since Ansar Dine, the main radical Islamist group in the north, recently seized control of the historic city of Timbuktu after ousting the Tuareg rebel faction that helped them invade the north. The Islamists are now requiring women to veil themselves and have banned popular pastimes like playing music and soccer.

Late last month, the group announced that a couple who had an adulterous relationship had been stoned to death in the town of Aguelhok.

Last month, the Security Council threatened sanctions against the Islamist fighters and condemned the destruction of sacred tombs in Timbuktu. It also indicated its willingness to consider an intervention force but stopped short of authorizing one.

On Tuesday, the reclusive leader of Ansar Dine, or "Defenders of the Faith," said he had faith in an ECOWAS mediation effort led by neighboring Burkina Faso.

Iyad Ag Ghali met with Burkina Faso's foreign minister, Djibril Bassole. Ag Ghali is known to have ties to al-Qaida in the Islamic Maghreb, the al-Qaida franchise operating in North Africa.