Sudan’s military has used chemical weapons on at least two occasions against the paramilitary group it is battling for control of the country, four senior United States officials said on Thursday.
The weapons were deployed recently in remote areas of Sudan, and targeted members of the Rapid Support Forces paramilitaries that the army has been fighting since April 2023. But U.S. officials worry the weapons could soon be used in densely populated parts of the capital, Khartoum.
The revelations about chemical weapons use came as the United States announced sanctions on Thursday against the Sudanese military chief, Gen. Abdel Fattah al-Burhan, for documented atrocities by his troops, including indiscriminate bombing of civilians, and the use of starvation as a weapon of war.
The use of chemical weapons crosses yet another boundary in the war between the Sudanese military and the R.S.F., its former ally. By many measures, the conflict has created the world’s worst humanitarian crisis, with as many as 150,000 people killed, over 11 million displaced and now the world’s worst famine in decades.
“Under Burhan’s leadership, the S.A.F.’s war tactics have included indiscriminate bombing of civilian infrastructure, attacks on schools, markets, and hospitals, and extrajudicial executions,” the Treasury Department said, using an acronym for Sudan’s armed forces.
The United Nations, allied nations and aid groups were notified on Wednesday night about the impending sanctions against General al-Burhan. The U.S. decision is considered a significant move against a figure seen by some as Sudan’s head of state, who also represents his country at the United Nations.
Aid groups fear that Sudan’s military could retaliate against the sanctions decision by further restricting aid operations in areas that are either in famine or sliding toward it.
It was not immediately clear what type of chemical weapons were used. Knowledge of the chemical weapons program was limited to a small group inside Sudan’s military, two of the U.S. officials said, speaking on the condition of anonymity to discuss sensitive security matters. But it was clear that General al-Burhan had authorized their use, they said.
Sudan’s ambassador to the United Nations, Al-Harith Idriss al-Harith Mohamed, denied the accusation. Sudan’s military “never used chemical or incendiary weapons,” he said in a text message, noting that Sudan is a member of the Organization for the Prohibition of Chemical Weapons.
“On the contrary, it’s the militia that used them,” he added, referring to the Rapid Support Forces.
Last week, the United States determined that the Rapid Support Forces had committed genocide in the war, and imposed sanctions on its leader, Lt. Gen. Mohamed Hamdan, for his role in atrocities against his own people. The United States also sanctioned seven companies based in the United Arab Emirates that traded in weapons or gold for the R.S.F.
Sudan’s military has been accused of using chemical weapons before. In 2016, Amnesty International said it had credible evidence of at least 30 likely attacks that killed and maimed hundreds of people, including children, in the western Darfur region. The organization published photos of children covered in lesions and blisters, some vomiting blood or unable to breathe.
As the United States debated punitive measures against General al-Burhan last week, the Sudanese authorities announced that they would maintain a major aid corridor through neighboring Chad, a move American officials saw as an effort to avoid the sanctions.
Two American officials said the United States detected numerous chemical weapons tests by Sudanese forces this year, as well as two instances in the past four months in which the weapons were used against R.S.F. troops.
The United States has also obtained intelligence that chemical weapons could soon be used in Bahri, in northern Khartoum, where fierce battles have raged in recent months as the two sides compete for control of the capital.
Last weekend, the Sudanese military secured a major victory when its forces recaptured the key city of Wad Madani, the capital of Sudan’s breadbasket region, from the R.S.F. Residents who celebrated the victory said the R.S.F.’s yearlong occupation of the city had led to widespread abuses and pushed a fertile state toward famine.
Combined with the American determination that the Rapid Support Forces had committed genocide, the recapturing of Wad Madani suggested that Sudan’s military was gaining momentum on the battlefield and support among the public.
But in recent days, reports have emerged of vicious reprisals by Sudanese troops against suspected R.S.F. collaborators in the area, including torture and summary executions. The United Nations said it was “shocked” by the reports and ordered an investigation into the killings.
Although the use of chemical weapons was a major element in the decision to level sanctions against General al-Burhan on Thursday, the action was also in response to other atrocities, like bombing raids that have killed dozens of civilians at a time, as well as attacks on hospitals and other buildings that are protected under the laws of war.
Two American officials said the United States was caught in a bind: In order to protect the source and method of the intelligence used to determine that chemical weapons had been used in Sudan, the United States did not want to reveal details about the strikes, the officials said.
But U.S. officials also wanted to move against General al-Burhan before President-elect Donald J. Trump is inaugurated on Monday. Under U.S. law, Congress must be notified of the discovery of chemical weapons use, and officials said that members of Congress are expected to be briefed on the issue in a classified hearing next month.
In addition to targeting General al-Burhan, the sanctions announced on Thursday also targeted a man described as a Sudanese arms supplier, and a company based in Hong Kong. A U.S. official said the company had been used to supply Sudan’s military with Iranian-made drones.
