Kidnappers killed five Chinese oil workers out of nine they had been holding hostage in central Sudan for more than a week, the Sudanese Foreign Ministry said on Monday.
The ministry blamed the Justice and Equality Movement, a Darfur rebel group, for seizing and killing the Chinese.
"Five were murdered. Two were able to escape with minor injuries," ministry spokesman Ali al-Sadig said. The kidnappers were still holding two of the workers hostage.
"This incident happened without any provocation," he told Reuters. JEM leaders were not available for comment.
The nine-day kidnapping saga was the third such incident in the energy-producing state of South Kordofan in the past year.
Analysts said the underdeveloped region could become another violent flashpoint in Sudan. If the JEM had indeed carried out the kidnapping, it showed how violence in neighbouring Darfur could spread.
The nine workers were snatched near a small oil field where they were doing contract work for the Greater Nile Petroleum Operating Company (GNPOC). The company is a consortium led by China's CNPC that also includes India's ONGC, Malaysia's Petronas and Sudan's state-owned Sudapet.
Sadig said the kidnappers had demanded that Chinese oil firms leave the region.
"We call on the international community to condemn the Justice and Equality Movement," he said. "Nobody is condemning it for its actions."
The Chinese embassy in Khartoum could not be reached for comment, but China's Xinhua news agency said the embassy "strongly condemned" the killings.
The embassy also urged local authorities to continue efforts to find the two missing workers and to take steps to safeguard Chinese citizens in Sudan.
The Darfur rebel group has not confirmed or denied its involvement in the incident. It said it had forces in the area and warned that oil workers were legitimate military targets.
JEM seized five oil workers -- an Egyptian, an Iraqi and three Sudanese -- in October 2007 but released them later.
Local tribesmen have identified the head of the kidnappers as a man called Fudeili, a member of a sub-clan of the Arab al-Misseriya tribe called Awlad Omran.
Local officials said the kidnappers, whom one diplomat familiar with the issue called disaffected locals, probably wanted oil money.
Abdul-Rasoul al-Nur, a former governor of Kordofan and a Misseriya leader, said his tribe condemned the killings.
"Even if the demands (of the captors) were just, the wrong methods obstruct reaching those just demands. This is a huge mistake," he told Reuters.
Sudanese officials said on Wednesday they had pinpointed the location of the hostages but wanted to secure their release peacefully.
According to GNPOC's website, the consortium produces more than 300,000 barrels of crude per day (bpd) in Sudan's Blocks 1, 2 and 4. Sudan produces about 500,000 bpd of crude and China is the biggest foreign investor in the country.
(Additional reporting by Firouz Sedarat in Dubai; Editing by Giles Elgood)