China has sent a team of officials to Sudan to secure the release of 29 Chinese workers held by rebels in South Kordofan, its foreign ministry said.
They were taken by the Sudan People's Liberation Movement-North (SPLM-N) forces on Saturday.
''The Chinese side calls on all parties concerned to exercise calm and restraint,'' Liu Weimin, a ministry spokesman said on Tuesday.
The team left for Sudan on Monday night, the statement said.
The ministry also called for the release of the workers as soon as possible in the statement on its website.
Sudanese state media had reported earlier that security forces had freed 14 of the workers.
But rebel spokesman Arnu Ngutulu Lodi denied this, saying that South Kordofan state governor Ahmad Mohamed Harun, whom the report quoted, ''was lying''.
"They are okay. They are doing well," Mr Lodi told Agence France Presse news agency on Monday. He said that the workers would be released when ''the security situation allows''.
Meanwhile, another 34 workers from the same company have arrived in Khartoum. The group included 17 Chinese employees who were working at a camp near Al-Abbasiya town that was attacked by the rebels.
According to the report from China's Xinhua news agency, there were 47 Chinese workers at the camp when the attack took place. Of these 29 were abducted and 18 fled, it said. The Sudanese army found 17 of those who fled nearby and one remains still missing.
The other 17 workers who have gone to Khartoum were working at another camp, Chinese media said.
They were received at the airport by the Chinese ambassador to Sudan, Luo Xiaoguang and Sudanese officials.
"This incident is individual and does not affect the bilateral ties between Sudan and China," said Mr Luo. China, which is the biggest buyer of oil from Sudan, is a key trading partner of the country.
A spokesman from the Sudan People's Liberation Movement-North (SPLM-N) rebels told the AFP news agency on Sunday that the workers were caught in crossfire with the army.
South Kordofan is one of three areas hit by conflict since South Sudan became independent from Sudan in July.
Abyei and Blue Nile along with South Kordofan lie along the loosely demarcated border between Sudan and South Sudan.
The SPLM-N fought alongside former rebels who led South Sudan to independence in July 2011 - the two groups deny charges from Khartoum that they are still working together.
Sudan's government has denied accusations from human rights groups that it is carrying out a campaign of ethnic cleansing against the Nuba community seen as supporting the SPLM-N.
Last week, Sudan also denied that it had bombed refugees who had fled the conflict into South Sudan.
China's Ministry of Commerce has warned firms in Sudan of security risks.
''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.