Heavy clashes and artillery fire have erupted across Sudan’s capital Khartoum and residents reported air strikes soon after the end of a 24-hour ceasefire that brought a brief lull to eight weeks of fighting between rival military factions.

Witnesses said the fighting on Sunday between the army and the paramilitary Rapid Support Forces (RSF) was some of the heaviest for weeks.

It included ground battles in the densely populated neighbourhood of Haj Youssef in Bahri, one of three adjoining cities, along with Khartoum and Omdurman, that make up the capital around the confluence of the River Nile.

Saudi Arabia and the US, which brokered the ceasefire at talks in Jeddah, said the truce had allowed delivery of some vital humanitarian assistance and confidence building measures.

“However, there were violations, and, following the expiration of the short-term ceasefire, facilitators have been deeply disappointed by the immediate resumption of intense violence, which we strongly condemn,” they said in a statement.

Just after the ceasefire expired at 6am local time, witnesses said clashes and artillery fire resumed in the north of Omdurman.

They also reported fighting in southern and central Khartoum, and in Shambat along the Nile in Bahri up to the strategic Halfiya bridge, which crosses to Omdurman.

War between Sudan’s army and the paramilitary Rapid Support Forces (RSF) broke out on April 15 over tensions linked to an internationally backed plan for a transition towards civilian rule.

The conflict has killed hundreds of civilians and displaced more than 1.9 million, triggering a major humanitarian crisis that threatens to spill across a volatile region.

Fighting has been concentrated in the capital, much of which has become a war zone plagued by looting and clashes.

But unrest has also flared elsewhere including the western region of Darfur, already suffering from a conflict that peaked in the early 2000s.

Residents and activists have reported a further deterioration in recent days in El Geneina, near the border with Chad, and new waves of attacks by Arab nomadic tribes with ties to the RSF.

Among those killed were a number of human rights activists, lawyers and doctors, according to the Darfur Bar Association, which monitors the conflict in the region.

The city has been largely cut off from telephone networks for several weeks.