A group of Chinese workers "kidnapped" by rebels in southern Sudan 11 days ago have been freed and flown to Kenya, the foreign ministry said on Tuesday.

"The Sudanese authorities allowed a Red Cross plane to take them from Kauda to Nairobi ... this Tuesday morning where they were given to the Chinese embassy there," the statement said.

The statement did not give the number of Chinese freed.

The Kauda area in the Nuba Mountains of South Kordofan state has been the scene of fighting since June between government troops and rebels formerly aligned with the rulers of now independent South Sudan.

Sudan People's Liberation Movement-North (SPLM-N) spokesman Arnu Ngutulu Lodi told AFP he would comment later Tuesday, but the release comes a day after he said he expected the 29 Chinese workers to be released "very soon."

Lodi said on Monday the rebels were in communication with the Chinese government, although not through a six-member mission sent by Beijing to Khartoum to help secure a release.

The captives, who were involved in a road-building project in South Kordofan, had been held since January 28 when the SPLM-N destroyed a Sudanese military convoy between Rashad town and Al-Abbasiya and took over the area, the rebels said.

A spokeswoman for the Geneva-based International Committee of the Red Cross (ICRC) declined to comment except to say: "We are not involved in negotiations" over the Chinese.

The SPLM-N maintained that all 29 Chinese were safe during their captivity.

According to China's official Xinhua news agency, the workers were taken after a rebel attack on their camp.

It reported on Monday that Beijing had been informed by Sudanese authorities that the body of one Chinese, who went missing in the attack, had been found. That person was apparently not among the 29 captured.

Sudanese official media carried similar reports citing the South Kordofan state government.

Chinese embassy officials in Khartoum could not be reached on Tuesday.

Last week, SPLM-N chairman Malik Agar met a Chinese diplomat and asked Beijing to use its influence with Khartoum to help badly needed aid to reach the war zone, Lodi said.

Agar held the talks in Addis Ababa with the Chinese ambassador to Ethiopia.

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

Sudan has severely restricted the work of foreign relief agencies in South Kordofan and nearby Blue Nile state, where a similar war began in September.

About 30,000 people fled when the rebels took control of villages in the Al-Abbasiya area on January 28, the United Nations said.

The UN has backed statements by the United States that there could be a famine unless urgent aid is allowed to enter South Kordofan and Blue Nile.