CAIRO – A leading medical group warned on Tuesday of a rising number of cholera cases in war-torn Sudan as a new outbreak of the waterborne disease grips the country, and said its teams have treated hundreds of patients in the region of the capital, Khartoum.

Joyce Bakker, the Sudan coordinator for Doctors Without Borders — also known as Médecins Sans Frontières or MSF — said that the alarming spike began in mid-May, with Khartoum’s twin city, Omdurman, as the epicenter.

She said MSF treated almost 2,000 suspected cholera cases in the past week alone. There were no immediate official figures of fatalities from cholera in this latest outbreak, though an aid worker said he was told on Monday of 12 people dying of cholera.

In March, MSF said that 92 people had died of cholera in Sudan’s White Nile State, where 2,700 people had contracted the disease since late February.

Sudan plunged into war more than two years ago, when tensions between the Sudanese army and its rival paramilitary Rapid Support Forces group, or RSF, exploded with battles in Khartoum and across the country.

Since then, at least 20,000 people have been tallied as being killed, though the number is likely far higher, and the African nation has been engulfed by what the United Nations says is the world’s largest humanitarian crisis.

More than 14 million people have been displaced and forced from their homes and disease outbreaks, famine and atrocities have mounted as the country entered its third year of war.

Sudan’s Health Minister Haitham Ibrahim said on Saturday that the recent increase in cholera cases is estimated to average 600 to 700 per week, over the past four weeks.

He attributed the surge to the return of many Sudanese to the Khartoum region — people who had fled their homes to escape the fighting and who are now coming back. Their returns have strained the city’s dwindling water resources, he said.

Last week, the Sudanese military said it had regained control of the Greater Khartoum area from the paramilitary forces.

On Monday, Mohanad Elbalal, co-founder of the Khartoum Aid Kitchen, said he was told that 12 people had died of cholera in Omdurman, including a relative of one of his kitchen staff.

Bakker, the MSF coordinator, said Tuesday that the group’s treatment centers in Omdurman are overwhelmed and that the “scenes are disturbing.”

“Many patients are arriving too late to be saved,” she said. “We don’t know the true scale of the outbreak, and our teams can only see a fraction of the full picture.”

She called for a united response, including water, sanitation and hygiene programs and more treatment facilities.