For the second consecutive year Sudan is in the grip of a cholera outbreak that has left at least 28 people dead in the last month as rains fall in areas crammed with those fleeing the country's 16-month-old war, officials said.

Since July 22, when the current wave began, 658 cases of cholera have been recorded across five states, World Health Organization (WHO) country director Shible Sahbani told Reuters in Port Sudan.

With much of the country's health infrastructure collapsed or destroyed and staffing thinned by displacement, 4.3% of cases have resulted in deaths, a high rate compared to other outbreaks, Sahbani said.

Some 200,000 are at high risk of falling ill, he said.

The war between the army and the paramilitary Rapid Support Forces (RSF) has created one of the world's largest humanitarian crises and displaced more than 10 million people inside Sudan and beyond its borders.