Rebels in Sudan claimed they held 29 Chinese workers following an firefight with Sudanese armed forces. [File photo]

29 Chinese workers have been held by rebels in Sudan after an attack by the rebels with Sudanese armed forces. However, the Chinese Embassy in khartoum said that 27 Chinese nationals are missing.

The workers were working for a Chinese company operating in the field of roads at South Kordofan state which has been recently witnessing armed clashes.

The camp the workers were staying in was attacked by militants in Sudan's South Kordofan state on Saturday afternoon, the Foreign Ministry said on Sunday.

But the ministry did not give more details. It urged Sudan to take measures to rescue the workers and ensure the safety of all Chinese citizens in the country, said Liu Weimin, ministry spokesman.

"Currently the Sudanese government is doing their utmost to locate and rescue the missing Chinese nationals and has increased protection for other Chinese nationals in Sudan," he added.

Wang Zhiping, spokesman for Sinohydro Corp Ltd, the workers' employer, said that managers were among those missing.

"We have contacted the families of all those missing and tried to comfort them," he said.

The Chinese embassy in Sudan said 27 workers are missing, according to media reports.

Rebels said they have captured 29 workers after a battle with government forces.

Nine members of the Sudan Armed Forces were also being held, Arnu Ngutulu Lodi of the Sudan People's Liberation Movement-North, told AFP.

"Yes, we have captured them," he said. "I want to assure you right now they are in safe hands." None of the Chinese workers were wounded, he said.

The workers were captured after rebels destroyed a military convoy between Rashad town and Al-Abbasiya in the northeast of the province, which has been hit by conflict since South Sudan became independent from Sudan in July.

There is growing international concern over the situation in South Kordofan and nearby Blue Nile state.

"It could be just unfortunate that the Chinese workers were captured during fighting between rebels and government forces," said Li Xinfeng, a researcher of African studies at the Chinese Academy of Social Sciences. "Fighting has broken out frequently in recent months.

"The unstable political situation is the root reason for attack, and the possibility cannot be excluded that the rebels are targeting Chinese as a bargaining chip with the government," he said.

China is a key investor in Sudan, a regional expert said.

"As a major buyer of Sudanese oil, China has increased investment in infrastructure, agriculture and manufacturing in recent years," said He Wenping, director of the African studies department at the Institute of West Asian and African Studies under the Chinese Academy of Social Sciences.

There have been attacks before but nothing as big as this, she said.

Chinese companies in Sudan need better protection to be provided by both local government and security services, she added.

With China's growing global influence many citizens are working in politically unstable areas.

Four Chinese workers were kidnapped by an unknown group in Colombia in June. Efforts to secure their release are ongoing.