The Chinese team had been working for the China National Petroleum Corporation (CNPC) at the time of their capture.

The oilfield is run by the Greater Nile Petroleum Operating Company (GNPOC), a consortium of four oil companies from China, India, Malaysia and Sudan.

The kidnappers released one of the Sudanese drivers shortly after the men were abducted.

An unidentified diplomatic source said shortly after the attack that members of the Arab Messeria tribe had carried out the abduction in an attempt to win a greater share of the region's oil revenue.

However, al-Sadiq said the kidnappers were members of a Darfur group called the Justice and Equality Movement (Jem).

The abduction is the third such incident over the past year in the region, the source of a large part of Sudan's oil wealth.