KHARTOUM  - Rebels still hold 29 Chinese workers in Sudan, Beijing's official news agency reported on Monday, as the Sudanese military said the captives are being held hostage.Xinhua, citing Beijing's embassy in Khartoum, said that while 29 remained captive, 17 Chinese were moved to safety by the Sudanese army when rebels attacked the workers' camp on Saturday.Insurgents from the Sudan People's Liberation Movement-North (SPLM-N) in South Kordofan state told AFP on Sunday that they had captured 29 Chinese, who were unharmed and "in safe hands"."They are held hostage by SPLM," said the Sudanese army spokesman Sawarmi Khaled Saad. He said soldiers were searching for the captives, "and SPLM are responsible for their safety".The rebels could not be reached on Monday, and numerous attempts to contact Chinese embassy officials have been unsuccessful.China confirmed on Sunday that some of its nationals had "gone missing" after rebels attacked the camp of a Chinese company, Xinhua reported.It quoted an embassy official as saying more than 20 Chinese were unaccounted for, a figure also given by a senior executive at Power Construction Corp of China, their employer.China's commerce ministry on Monday urged companies and personnel operating in Sudan to strengthen security after the incident."The commerce ministry reminds relevant companies and personnel to pay close attention to changes in the local security situation, strengthen their own security and ensure the safety of people and property," it said in a statement.SPLM-N spokesman Arnu Ngutulu Lodi earlier told AFP the Chinese were captured along with nine members of the Sudan Armed Forces (SAF) when the rebels destroyed a Sudanese military convoy between Rashad town and Al-Abbasiya in the northeast of the province, which has been at war since June.Lodi denied the Chinese had been kidnapped.They were involved in a road-building project, the executive from Power Construction Corp told Xinhua.China is Sudan's major trading partner, the largest buyer of Sudanese oil, and a key military supplier to the regime in Khartoum.There is growing international concern over the situation in South Kordofan and nearby Blue Nile state, where a similar conflict broke out in September.The government is fighting ethnic minority insurgents once allied to the former rebels who now rule South Sudan.The South gained independence from Khartoum last July after decades of civil war.Food shortages would become critical without substantial aid deliveries into South Kordofan and Blue Nile by March, the US ambassador to the United Nations, Susan Rice, has said.Khartoum has severely restricted the work of foreign relief agencies in the war zones.It cited security concerns and also accused aid workers of using United Nations flights to deliver arms and ammunition to the rebels -- a claim for which the UN's top humanitarian official said there was "no evidence".Princeton Lyman, the US administration's special envoy for Sudan, told reporters last week the situation is so dire Washington has warned Khartoum it would consider ways for aid to be sent in without Sudanese government approval.