An United Nations  helicopter crashed in the northern region of South Sudan, killing three crew members and injuring a fourth, the UN mission there said.

The cause of the crash was not immediately known.

The incident happened at about 2:28 p.m. local time when the UN Mission in South Sudan lost contact with one of its Mi-8 helicopters, which was on a routine cargo flight from the city of Wau in northwestern South Sudan to the oil town of Bentiu in northern Unity State.

The aircraft crashed about 10 kilometers (6.2 miles) south of Bentiu.