At least 18 people have died of cholera in war-torn South Sudan, the health ministry said Tuesday, as it declared an outbreak of the highly contagious infection.

The outbreak began in crowded United Nations bases in the capital Juba where tens of thousands of people have been sheltering for the 18-month long civil war, with cases reported elsewhere in the city, Minister of Health Riek Gai Kok told reporters. Some 140 people died in an outbreak last year.