Two civilian members of the joint United Nations-African Union peacekeeping mission in Darfur who were held hostage for more than 100 days have been released, the U.N. said Sunday.

U.N. Secretary-General Ban Ki-moon's office released a statement saying he was "deeply gratified" to learn of the development.

The two staffers, a man and a woman, were taken at gunpoint in West Darfur on Aug. 29. The abductors have not been publicly identified.

The United Nations has been involved in delicate diplomacy to get cooperation on the issue from Sudan's President Omar al-Bashir.

The International Criminal Court issued an arrest warrant for the Sudanese leader in March on charges of orchestrating war crimes and crimes against humanity in Darfur.

But a week ago, Ban called al-Bashir "on humanitarian grounds" to seek help in freeing the two hostages, one of whom was said by the U.N. to be gravely ill.

U.N. spokesman Martin Nesirky had said it was the first call between the secretary-general and al-Bashir since the arrest warrant was issued. Al-Bashir has refused to recognize the tribunal's authority.

The two abductees were civilians assigned to the U.N.-AU peacekeeping force, known as UNAMID.

The United Nations gave no further detail on the circumstances of their release except to say they "are now free and in the care of UNAMID."

"The Secretary-General commends the efforts of UNAMID and the Government of Sudan in securing the freedom of the abductees," said the U.N. statement.

"He wishes to underscore the importance of the peacekeeping and humanitarian work being undertaken by the United Nations in Darfur."

"The Secretary-General also reiterates that the primary responsibility for the safety and security of all humanitarian and peacekeeping personnel lies with the Host Government," referring to al-Bashir's government in Khartoum.

The war in Darfur began in 2003 when rebel groups took up arms against the government, complaining of discrimination and neglect. U.N. officials say up to 300,000 people have died and 2.7 million have fled their homes.

Last weekend five UNAMID peacekeepers from Rwanda were killed in two separate incidents, bringing the total number of blue helmets who have lost their lives in Darfur since the force deployed at the start of 2008 to 22.

Almost two years after being set up, UNAMID has still only reached 69 per cent of its authorized troop strength of 19,555, and 4,449 police.