Fighting is continuing in the capital of Khartoum, despite promises of a ceasefire between the two sides.

The intense fighting, which started more than two weeks ago, triggered an exodus of tens of thousands of Sudanese to neighbouring countries including Egypt, Chad and the Central African Republic.

"UNHCR, with governments and partners, is preparing for the possibility that over 800,000 people may flee the fighting in Sudan for neighbouring countries.

"We hope it doesn’t come to that, but if violence doesn’t stop we will see more people forced to flee Sudan seeking safety." UN refugee agency UNHCR chief Filippo Grandi tweeted.

The UN's Humanitarian Co-ordinator in Sudan Abdou Dieng said the conflict was turning into a full blown catastrophe.