Four Chinese workers who were abducted at the weekend in Sudan's western Darfur region have been freed and sent to the capital Khartoum.

Luo Xiaoguang, the Chinese ambassador to Sudan, and members of the Chinese community resident in Sudan were at the airport to meet them on Thursday.

Unknown gunmen had kidnapped the Chinese - one engineer and three drivers working for a road construction company - together with five Sudanese colleagues on Saturday near al-Fasher in North Darfur.

The ambassador said the kidnapping should not put relations between the two countries in a negative light.

"I think that this sad incident will not affect the ongoing friendly relations between China and Sudan, and will not affect the fruitful co-operation between China and Sudan." said Luo.

Mohammed Suleiman Rabih, commissioner of al-Kuma administration in North Darfur, said the Chinese had been handed over to the international peacekeeping force UNAMID on Wednesday.

UNAMID confirmed the Chinese had arrived at a one of its compounds in South Darfur, but would not give further details.

US embargo

Gunmen often kidnap foreigners in Darfur to demand a ransom for their release.

China is Sudan's biggest ally and largest investor in the oil industry there, as it is also in Khartoum's arch-rival South Sudan.

Chinese firms are ever-present in Sudan, as most Western firms shun the country due to a US trade embargo.

Sudan has sought to assure Beijing that it would protect its firms after rebels in Sudan's main oil-producing state of South Kordofan kidnapped 29 Chinese workers in January 2012. They were released almost two weeks later.

In December, a Sudanese court handed out life sentences to four Sudanese for killing a Chinese worker during a raid on a workers' oil camp, the state-linked Sudanese Media Centre said.

Beijing has tried to help Sudan overcome the loss of most oil reserves, the lifeline of the economy, when South Sudan became independent in 2011.

Last week, Sudan's Finance Minister Ali Mahmoud told the Reuters news agency that China had granted the country a $1.5bn loan at a time when Sudan is trying to stop a slide in its currency.