Sudan’s army has launched artillery and air strikes on the capital Khartoum in its biggest operation to retake territory there since the start of a 17-month war between it and the Rapid Support Forces, military sources said on Thursday.

Witnesses said heavy shelling and clashes erupted as army troops tried to cross bridges over the Nile linking the three neighbouring cities that make up the capital, Khartoum, Omdurman and Bahri.

The offensive by the army, which lost control of much of the capital at the start of the conflict, comes ahead of a speech by its commander, General Abdel Fattah al-Burhan, who is due to address the United Nations General Assembly in New York later.