Sudanese authorities on Tuesday released a senior member of the opposition Umma Party who was detained last month after the party reached a deal to cooperate with rebels.

Mariam al-Mahdi, deputy leader of the party led by her father Sadiq al-Mahdi, "has been released," Umma's youth leader Mohammed Mahdi said on his Facebook page.

Libya has accused Sudan of flying weapons to "terrorist" groups on its territory and declared Khartoum's military attache persona non grata, a government statement said.

According to the statement, received on Sunday by AFP, a Sudanese aircraft carrying ammunition destined for Libyan armed groups landed in the southern Kufra region on an unspecified date.

Iran's main cultural centre in the Sudanese capital was padlocked on Sunday, an AFP correspondent reported, and officials said the decision was final.

The Iranian flag still flew above the building on one of Khartoum's main roads across from the airport.

South Sudanese rights groups demanded Thursday an international arms embargo for their conflict-wracked nation, as millions of dollars worth of newly-bought weapons fuel an almost nine-month long civil war.

Iran on Wednesday denied its cultural centers in Sudan have been closed on the orders of Khartoum, saying Sudanese authorities would not want to damage relations.

"The embassy and the cultural and economic centers of Iran and Sudan are continuing with their normal activities in the two countries," said Deputy Foreign Minister Hossein Amir-Abdollahian, quoted by Fars news agency.

Sudan has ordered Iran to close its cultural centers and given their managers 72 hours to leave the country, an official said Tuesday, in a shock to generally close relations.

Warring forces in South Sudan traded blame Wednesday for the crash of a U.N. helicopter in which three crew died, although investigations have yet to confirm if it was shot down.

Sudan, Egypt and Ethiopia opened talks Monday to try to resolve a dispute over a hydro-electric dam being built by Addis Ababa on the Nile.

Cairo fears that Ethiopia's Grand Renaissance dam project could diminish its water supply.

Dozens of people have been killed in clashes between two Arab tribes in Sudan's troubled western region of Darfur, witnesses from the rival camps said on Wednesday.

A witness said at least 30 members of his Rezeigat tribe were killed in the fighting with Maaliya tribesmen over territorial claims in the Umm Rakuba district.

Attacks on aid workers reached a new peak in 2013, with 155 relief staff killed, and danger levels remain high this year, according to figures released Tuesday.