Fighting between Sudan's armed forces and the paramilitary Rapid Support Forces has entered a third week, raising concerns of a deepening humanitarian crisis in the region.

The two sides agreed to extend a ceasefire for another 3 days through Sunday. But gunshots and shelling were heard on Saturday in the capital Khartoum and elsewhere.

Sudan's health ministry says that 528 people have been killed since the violence erupted on April 15.

The RSF released a statement on Saturday saying that it had shot down an army warplane in the capital.

The army said in a social media post that it would never yield to rebels and the Sudanese people will be able to celebrate their victory soon.

Foreign nationals have been evacuated from the country through the northeastern city of Port Sudan and elsewhere.

A Saudi-flagged ship reportedly evacuated about 1,900 people -- citizens of Saudi Arabia and other countries -- on Saturday.

The United Nations expects nearly 100,000 refugees will flee Sudan to neighboring Chad. There are fears the mass exodus will further worsen the humanitarian crisis.