Authorities in Sudan are stepping up efforts to force the U.N.-African Union mission in Darfur to leave, threatening the supply of vital humanitarian aid deliveries.

UNAMID deployed to Darfur in 2007, its nearly 16,000 peacekeepers mandated to protect civilians and secure humanitarian assistance across an area the size of France.

Sudanese security forces have arrested two opposition figures who joined an alliance aimed at uniting opposition to the government, a member of one group that signed the document said Sunday.

The National Intelligence and Security Services (NISS) detained Farouk Abu Issa, head of the opposition National Consensus Forces (NCF), and civil activist Amin Makki Madani late Saturday, NCF official Siddig Youssif told AFP by telephone.

Sudan's foreign minister accused "foreign parties" of fueling fighting in Libya as he opened a meeting of neighboring countries Thursday aimed at ending more than three years of violence.

Libya has been gripped by lawlessness ever since the 2011 overthrow of Moammar Gadhafi and is awash with weapons left over from the NATO-backed uprising against his dictatorship. Rival governments and parliaments dispute power, with swathes of territory in the hands of powerful militia.

Sudanese opposition parties and rebels meeting in Addis Ababa agreed to form a new alliance Wednesday, one of the groups said, urging the creation of a transitional government in Khartoum.

The agreement is the first to include as wide a range of political parties and armed groups as it does, working together against the 25-year rule of President Omar al-Bashir.

Moscow is ready to host a conference on ridding the Middle East of weapons of mass destruction, Foreign Minister Sergei Lavrov said in Sudan on Wednesday.

"There should be a conference to remove weapons of mass destruction and put in place an agreement to make the Middle East a region free of nuclear weapons," Lavrov said before attending a forum on cooperation between Russia and the Arab League.

Russia plans to strengthen its military ties with Khartoum, Foreign Minister Sergei Lavrov said on Wednesday during a visit to internationally isolated and sanctions-hit Sudan.

"We have a project and a plan to develop military cooperation in a way that will not disturb the balance of power in the region," Lavrov said at a news conference after meeting his Sudanese counterpart Ali Karti.

Sudanese President Omar al-Bashir Sunday called for a "clear program" for the U.N.-African Union mission in Darfur to leave, saying the peacekeepers had become a "burden".

Bashir's government is locked in a dispute with UNAMID over its investigation of reports Sudanese troops raped 200 women and girls in a Darfur village in October.

Sudanese President Omar al-Bashir Sunday called for a "clear programme" for the U.N.-African Union mission in Darfur to leave, saying the peacekeepers had become a "burden".

Bashir's government is locked in a dispute with UNAMID over its investigation of reports Sudanese troops raped 200 women and girls in a Darfur village in October.

The U.N.-African Union mission in Darfur said Tuesday that Sudan has asked it to close its human rights office in Khartoum, as tensions rise over investigations into an alleged mass rape.

The mission's attempts to investigate charges that government troops raped 200 women and girls in the Darfur village of Tabit last month have angered Khartoum.

Sudan's government and rebels from Darfur opened talks late Sunday, as mediators pushed for a ceasefire to end over a decade of war and insurgents warned the country was close to "collapse".

African Union chief mediator Thabo Mbeki called for a cessation of hostilities between the government and two rebel factions, part of wider efforts to stem multiple rebellions across Sudan.