CAIRO (AP) — Cholera is spreading in war-torn Sudan, killing at least 388 people and sickening about 13,000 others over the past two months on Monday, health authorities said, as more than 17 months of fighting between the military and a notorious paramilitary group shows no sign of abating.

Artillery shelling hit an open market Monday in Omdurman, the sister city of the capital, Khartoum, killing at least 13 people and wounded more than 30 others, the health ministry said.

The disease is spreading in areas devastated by recent heavy rainfall and floods especially in eastern Sudan where millions of war displaced people sheltered.

The casualties from cholera included six dead and about 400 sickened over the weekend, according to Sunday’s report by the Health Ministry. The disease was detected in 10 of the country’s 18 provinces with the eastern Kassala and al-Qadarif provinces the most hit, the ministry said.

Cholera is a fast-developing, highly contagious infection that causes diarrhea, leading to severe dehydration and possible death within hours when not treated, according to the World Health Organization. It's transmitted through the ingestion of contaminated food or water.

The disease isn't uncommon in Sudan. A previous major outbreak left at least 700 dead and sickened about 22,000 in less than two months in 2017.

Sudan was plunged into chaos in April last year when simmering tensions between the military and a powerful paramilitary group, the Rapid Support Forces, exploded into open warfare across the country.

The fighting, which wrecked the capital, Khartoum, and other urban areas has been marked by atrocities including mass rape and ethnically motivated killings that amount to war crimes and crimes against humanity, especially in the western region of Darfur, according to the United Nations and international rights groups.

Monday's shelling hit the Sabrian market in Karari district in Omdurman, said Mohamed Ibrahim, the health ministry’s spokesman. He blamed the RSF on the attack.

It has killed at least 20,000 people and wounded tens of thousands others, according to the U.N. However, rights groups and activists say the toll was much higher.

The war also has created the world’s largest displacement crisis. More than 13 million people have been forced to flee their homes since the fighting began, according to the International Organization for Migration. They include over 2.3 million who fled to neighboring countries.

Devastating seasonal floods and cholera have compounded the Sudanese misery. At least 225 people have been killed and about 900 others were injured in the floods, the Health Ministry said. Critical infrastructure has been washed away, and more than 76,000 houses have been destroyed or damaged, it said.

Famine was also confirmed in July in the Zamzam camp for displaced people, which is located about 15 kilometers (10 miles) from North Darfur’s embattled capital of al-Fasher, according to global experts from the Famine Review Committee. About 25.6 million people — more than half of Sudan’s population — will face acute hunger this year, they warned.

Fighting, meanwhile, rages in al-Fasher, the last major city in Darfur that is still held by the military. The RSF has been attempting to retake it since the start of the year.

Last week, the paramilitary force and its allied Arab militias launched a new attack on the city. The military said its forces, aided by rebel groups, managed to repel the attack and kill hundreds of RSF fighters, including two senior commanders.