"We thank him for his service and call for an urgent cessation of violence in Sudan, and resumption of dialogue," he said.

Earlier, EU foreign policy chief Josep Borrell tweeted that the security of diplomatic premises and staff was a "primary responsibility" of the Sudanese authorities.

EU spokeswoman Nabila Massrali told AFP news agency the EU delegation had not been evacuated from Khartoum following the attack. Staff security was the priority and security measures were being assessed, she added.

US state department spokesman John Kirby said there were currently no plans to evacuate US personnel, despite ongoing security concerns and the closure of Khartoum's airport but he urged all Americans to treat the situation "with the utmost seriousness".

The conflict has forced many civilians to shelter in their homes amid fears of a prolonged conflict that could land the country in deeper chaos.

On Monday, clouds of smoke were visible above Khartoum's main airport, with TV showing images of fires and explosions. Army air strikes targeted RSF bases, some of which are embedded in residential areas.

Hospitals were shelled, doctors say. Damage was reported at al-Shab Teaching Hospital in Khartoum along with two other clinics.

The fighting is between army units loyal to the de facto leader, Gen Abdel Fattah al-Burhan, and the RSF, a notorious paramilitary force commanded by Sudan's deputy leader, Mohamed Hamdan Dagalo, better known as Hemedti.

Hemedti said on Monday that the international community must intervene, and branded Gen Burhan "a radical Islamist who is bombing civilians from the air". Gen Burhan has said he is willing to negotiate.

The two sides held a brief ceasefire on Sunday to allow the wounded to be evacuated, although it was not clear how strictly they had stuck to it.

The regional Intergovernmental Authority on Development, or Igad, will send the presidents of South Sudan, Djibouti and Kenya to the country to try to broker peace.

Igad's executive secretary, Nuur Mohamud Sheekh, told the BBC there were some signs that progress could be made.

"They are preparing to travel to Sudan to meet with the two leaders but they are engaging with them through back channel diplomacy, they are speaking to these leaders to cease hostilities, to stop the fighting and return to the negotiating table," he said.

"Both these leaders are agreeable to mediation, which by itself is a very positive development over the last few hours. Our leaders have experience when it comes to mediating in conflicts."

BBC