KHARTOUM, Sudan -- A Sudanese governor says that two Russian pilots who were held by gunmen in the country's restive western Darfur region since January have been freed, and that no ransom was paid.

Gov. Shartay Jaafar Abdul Hakam said in a statement released on Saturday the two had been working for the United Nations-African Union Mission in Darfur, or UNAMID, when they were abducted by an unidentified armed group on January 29 while heading from a market to the mission base in Zalenge town.

Hakam says the two are back in Khartoum and are now in the Russian Embassy. The semi-official Sudan Media Center quoted the governor as saying that the abductors had earlier demanded money for the pilots' release but that paying a ransom would have set a precedent that encourages kidnapping.

U.N. Secretary General Ban Ki-moon said he was "deeply gratified" by the release of the two Russian contractors and expressed his appreciation for the efforts made by the U.N. mission, Sudan and Russia in securing their safe return, according to a statement released Saturday by Ban's spokesman. He called on the Sudanese government to launch a full investigation of their abduction.