The US government has imposed sanctions on the head of Sudan's army and de facto president, Gen Abdel Fattah al-Burhan, the treasury department said.

He has been leading one of the two sides in the 21-month civil war that has killed tens of thousands, uprooted over 12 million and pushed the country to the brink of famine.

In a brief statement, the US accused Gen Burhan of "destabilizing Sudan and undermining the goal of a democratic transition".