KAMPALA, Uganda—China began deploying 700 soldiers to a United Nations peacekeeping force in South Sudan to help guard the country's embattled oil fields and protect Chinese workers and installations, a spokesman for the African nation's president said Tuesday.

The airlift of the Chinese infantry battalion to the South Sudanese states of Unity and Upper Nile, the site of the only operating oil fields still under the control of the central government in Juba, was expected to take several days, spokesman Ateny Wek Ateny said....