China's Ministry of Commerce on Monday warned Chinese firms in Sudan of security risks after rebels abducted 29 Chinese workers in the African country.

Chinese companies should closely monitor changes in the country's security situation and take stronger precautions to ensure the safety of lives and property, the ministry said in a statement.

Several Chinese nationals remain missing after rebels attacked a construction site camp belonging to China's Power Construction Corp. in Sudan's South Kordofan area on Saturday, the ministry said.

An official with the Chinese Embassy to Sudan said Monday the embassy has sent a four-person work group to assist Sudanese authorities rescue the 29 Chinese nationals who are still being held by the rebels.

There were altogether 47 Chinese workers in the camp when the rebels attacked. Seventeen of them fled the camp to nearby places to hide from the rebels and have been moved to a safe location by the Sudanese army, while one worker remains missing, said the official.