Sudanese rebels released 29 Chinese workers on Tuesday, ten days after kidnapping them in the main oil-producing state of South Kordofan where the army has been fighting insurgents, Sudan's foreign ministry said.
The incident had been an embarrassment for the Sudanese government, which is trying to boost investment from China, its main political and trade ally, as it seeks to overcome a severe economic crisis.
The rebel SPLM-North group said it had taken the construction workers for their own security after a battle with the Sudanese army in South Kordofan, which borders newly independent South Sudan.
But the workers had apparently become caught up in a dispute between Khartoum and rebels who are trying to attract attention to the plight of 417,000 civilians who have fled fighting in South Kordofan and Blue Nile, another Sudanese border state.
Khartoum has restricted access for aid workers and the United Nations in both states, triggering warnings by the United States that a famine could break out.
The 29 Chinese workers were flown out from Kauda in South Kordofan by the International Committee of the Red Cross (ICRC), the campaign group and Sudan's foreign ministry said.
The Sudanese foreign ministry affirms to the government and people of China that Sudan's government seeks to protect Chinese investments and workers involved in it, the ministry added in a statement.
The workers later arrived in Kenyan capital Nairobi safe and sound, China's official news agency, Xinhua, said, citing a statement from the Chinese foreign ministry.
SPLM-North rebel spokesman Arnu Ngutulu Lodi declined to comment.
SPLM-North leaders met Chinese officials in Ethiopia last week.
Both South Kordofan and Blue Nile are home to large communities who sided with the south during decades of civil war with Khartoum. Many say they have been marginalised by the Khartoum government since South Sudan declared independence in July under a 2005 peace deal.
The SPLM is now the ruling party in the independent south and dismisses Khartoum's accusations that it supports SPLM-North rebels across the border.
China is an ally of both north and south and the main buyer of South Sudanese oil as well the biggest investor in Sudan.
Western diplomats say China has the best chance of defusing tensions between Khartoum and Juba, which are locked in a row over sharing oil wealth, dividing up debt and ending violence on both sides of their shared boundary.
The kidnap was the third abduction of Chinese people in Sudan since 2004 and highlighted the risks to China's expansion in Africa in search of minerals and energy.
Beijing had faced immense pressure to secure the safe return of the abducted workers. State-owned newspapers called for more protection for China's workers overseas as the world's second-largest economy expands its investments around the globe.
The workers belonged to state-owned Sinohydro Corporation, a hydropower engineering and construction company.
Khartoum counts on China to boost investment as it seeks to overcome the loss of three-quarters of its oil production, that South Sudan took with it when it seceded.
Most Western firms shun Sudan due to a U.S. trade embargo imposed first in 1997 when Khartoum was hosting prominent militants such as Osama bin Laden.
SPLM-North is one of a number of rebel movements in underdeveloped border areas who say they are fighting to overthrow Sudanese President Omar Hassan al-Bashir and end what they see as the dominance of the Khartoum political elite.
(Writing by Ulf Laessing and Sui-Lee Wee, Editing by Ron Popeski)