(AFP) - The United States and Saudi Arabia on Sunday made a renewed push for truce talks between Sudan's warring generals as deadly fighting has raged into its eighth week.

Multiple ceasefires have been agreed and broken, and Washington slapped sanctions on the two warring generals last week, blaming both sides for the "appalling" bloodshed.

Envoys of Sudan's regular army and paramilitary Rapid Support Forces (RSF) have remained in the Saudi coastal city of Jeddah despite the earlier collapse of ceasefire talks, the kingdom's foreign ministry said.

The foreign mediators called for "the parties to agree to and effectively implement a new ceasefire, with the aim of building to a permanent cessation of hostilities", Riyadh said.

A five-day extension of a US- and Saudi-brokered truce formally expired on Saturday with no signs of the conflict abating and fears that the rival sides were poised for an escalation.

Upwards of 1,800 people have been killed, according to the Armed Conflict Location and Event Data Project, and the UN says 1.2 million have been displaced with more than 425,000 fleeing abroad.

The RSF on Sunday claimed it had shot down a fighter jet after the army "launched an audacious airborne assault upon our forces' positions" in northern Khartoum.

A military source told AFP a Chinese-made jet crashed near Wadi Seidna base north of Khartoum because of a "technical malfunction".

Witnesses said they saw an aircraft travelling from the south to the north of the capital with flames erupting from it.

Other witnesses spoke of air strikes on RSF positions in the east of the city, with some civilian casualties reported.

- 'Disaster zone' -

The fighting erupted on April 15 in the Sudanese capital between the army led by de facto leader Abdel Fattah al-Burhan and the RSF commanded by his deputy-turned-rival Mohamed Hamdan Daglo.

Deadly battles have since gripped Khartoum and the war-scarred Darfur region in the west, forcing residents to flee or camp out for weeks as supplies of food and other vital goods have been depleted.

The governor of West Darfur, Khamis Abakar, said Sunday there was "complete lawlessness" in the state.

"Armed men have taken over everything, and the situation is completely out of control," he said.

Darfur governor Mini Minawi, a former rebel leader now close to the army, on Twitter denounced "looting" by armed groups, declared Darfur a "disaster zone" and appealed for help from the community international.

Sunday's Saudi statement comes two days before US Secretary of State Antony Blinken is due to arrive in the Gulf kingdom, with discussions on Sudan expected to be on the agenda.

The last truce was agreed to allow desperately needed humanitarian aid into areas of Sudan ravaged by the fighting, but like all those that preceded, the accord was routinely violated by both sides.

The Sudanese army on Wednesday withdrew from the talks in Jeddah.

A day later, the US-Saudi mediators declared the talks officially suspended, with Washington saying it was ready to resume the talks once the parties were "serious" about a ceasefire.

Both Burhan and Daglo have pledged repeatedly to protect civilians and secure humanitarian corridors.

But civilians reported escalated fighting after the army quit the Jeddah talks, including one army bombardment Thursday that a committee of human rights lawyers said killed 18 civilians in a Khartoum market.

Some 25 million people -- more than half Sudan's population -- are now in need of aid and protection in what was already one of the world's poorest countries before the conflict, according to the UN.

© Agence France-Presse