FILE PHOTO: The United Nations emblem is seen in the U.N. General Assembly hall during the 72nd United Nations General Assembly at U.N. headquarters in New York, U.S., September 22, 2017. REUTERS/Lucas Jackson

GENEVA (Reuters) - A storm ravaging southern Africa is possibly the worst weather-related disaster ever to hit the southern hemisphere, with 1.7 million people in the path of the cyclone in Mozambique and 920,000 affected in Malawi, U.N. officials said on Tuesday.

Storm surge floods up to 6 meters deep had caused “incredible devastation” over a huge area, World Food Programme regional chief Lola Castro said. The Buzi river had burst its banks, killing hundreds, and there was risk of more flooding in the Buzi, Pungoe and Save river basins in the next 72 hours.