BEIJING, Oct. 28 (Xinhua) -- China on Tuesday condemned the killing of four Chinese workers who were kidnapped in Sudan, urging the country to take all measures to ensure the safety of Chinese nationals.

    "We feel strong indignation and condemn the terrorist act by the kidnappers on unarmed Chinese company staff," Foreign Ministry spokeswoman Jiang Yu told a regular press conference.

    The Chinese government had expressed condolences to the victims' families, she said.

    Sudanese officials earlier reported to the Chinese embassy in Sudan that five of the nine kidnapped workers were killed on Monday, with two rescued and two missing. It revised the numbers late Tuesday afternoon, saying four were killed, four were rescued and the other was still missing, according to the Foreign Ministry.

    The nine workers from the China National Petroleum Corporation (CNPC) were kidnapped from an oil field near the western Sudanese region of Darfur on Oct. 18.

    The Chinese embassy said they were taken by unknown militants at the Southern Kordofan State, but no armed group had claimed responsibility for the kidnapping.

    President Hu Jintao and Premier Wen Jiabao had ordered the Foreign Ministry to do its utmost to rescue the trapped.

    The Chinese embassy in Sudan started holding intensive contacts and consultations with the Sudanese authorities.

    Liu Guijin, the Chinese government's special representative on the Darfur issue, arrived in Khartoum on Oct. 24.

    Jiang said the Foreign Ministry had urged the joint working group in Sudan, composed of embassy and CNPC officials, to continue efforts to ensure the safe return of the men.

    "The Chinese Foreign Ministry and other departments have made the utmost efforts for their return," Jiang said.

    She urged Sudan to continue to rescue the missing worker while ensuring his safety.

    She called on Sudan to "punish the murderers, and take all effective means to guarantee the safety of the Chinese workers in Sudan and their properties".

    Jiang also said China valued friendly relations with Sudan, and the cooperation between the two countries was mutually beneficial.