Armed militants killed two security staff and kidnapped a Chinese, an Algerian and a Sudanese worker in an attack on an oil field in Sudan's West Kordofan state, army spokesman Al-Sawarmi Khalid Sa'ad said on Saturday.
Security forces are still tracing the perpetrators, he added.
West Kordofan is the main oil-producing state in Sudan. It has faced several attacks by armed militants attempting to disrupt production.
The main rebel group active in the area, the Justice and Equality Movement, denied any involvement in the latest incident.
(Reporting by Khaled Abdel Aziz, writing by Asma Alsharif; editing by Mark Trevelyan)