China on Tuesday called for the immediate release of 29 Chinese workers held by Sudanese rebels, as it dispatched a team to the African nation to help defuse the situation.

"China calls on all sides to remain calm and exercise restraint, ensure the safety of Chinese personnel and quickly release the Chinese personnel out of humanitarian concerns," foreign ministry spokesman Liu Weimin said.

Beijing on Monday dispatched a team to Sudan led by foreign ministry officials to help resolve the standoff, he added in a statement posted on the ministry's website.

The workers were captured when rebels in the South Kordofan state attacked their camp on Saturday. They have been described as hostages by the military but rebels say they were side victims of fighting with government troops.

"They are okay. They are doing well," said Arnu Ngutulu Lodi, spokesman for the rebel Sudan People's Liberation Movement-North (SPLM-N).

"We are very concerned about their security and safety."

There is growing international concern over the situation in South Kordofan, where the government is fighting ethnic minority insurgents once allied to the former rebels who now rule South Sudan.

The South gained independence from Khartoum in July last year after decades of civil war.

The Chinese workers were involved in a road-building project in South Kordofan, and while 29 remain captive, 17 others have been moved to safety by the Sudanese army, China's official Xinhua news agency said.

China is Sudan's major trading partner, the largest buyer of Sudanese oil, and a key military supplier to the regime in Khartoum.