Fighting raged in Sudan on Friday, despite rival forces agreeing to extend a truce aimed to stem nearly two weeks of warfare that has killed hundreds and caused widespread destruction.

In the capital Khartoum, where foreign nations are scrambling to organize mass evacuations of their citizens, Turkey's defence ministry said a military transport aircraft came under fire.

Witnesses reported mass looting as gunmen fired rockets in bitter urban battles in the western Darfur region.

There have been multiple truce efforts since fighting broke out on April 15 between Sudan's army led by General Abdel Fattah al-Burhan and the paramilitary Rapid Support Forces (RSF) commanded by his former deputy and fellow coup leader Mohamed Hamdan Daglo. All have failed.

On Thursday, the two sides agreed to extend a repeatedly broken ceasefire for three more days.

The United States, Saudi Arabia as well as the African Union, the United Nations and others welcomed the rival generals' "readiness to engage in dialogue" in a bid to create a "more durable cessation of hostilities and ensuring unimpeded humanitarian access".

Since a power struggle between Burhan and Daglo erupted into violence, fighter jets have pounded RSF positions with air strikes in densely packed districts of Khartoum, as fighters on the ground exchanged volleys of artillery and heavy machine gun fire.

In some parts of the city of some five million people, trenches have been dug as gunmen battle each other street by street.

At least 512 people have been killed and 4,193 wounded in the fighting, according to health ministry figures, although the real death toll is likely much higher.