Nine Chinese oil workers have been kidnapped in Sudan, a Chinese diplomat in the capital, Khartoum, has said.

The men, and their two Sudanese drivers, were abducted, apparently by tribe members seeking greater oil wealth, in Kordofan state.

The diplomat said the men, working for the China National Petroleum Corporation (CNPC),  were taken near the disputed central oil region of Abyei on Sunday.

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.

An unidentified diplomatic source told the Reuters news agency: "One driver was released and handed over a note by the captors demanding a settlement through a share of oil production."

The source said that members of the Arab Messeria tribe had carried out the attack because they want a greater share of the region's oil revenue.

Li Chengwen, the Chinese ambassador to Sudan, said: "We are doing our best efforts to find them."

It is the third time within the last year that oil workers have been kidnapped in the region, the source of a large part of Sudan's oil wealth.

Officials say Sudanese forces have been deployed and are searching for the men, but no contact had been made with the kidnappers.