"Based on available evidence and data from field measurements, health surveillance systems and official medical reports... there is no evidence of chemical or radioactive contamination in Khartoum state," the health ministry said in a report released this week.

The ministry said the report was based on field tests and forensic reviews carried out since April, when the army regained control of the capital from the paramilitary Rapid Support Forces (RSF).

In June, Washington imposed sanctions on the army-backed government, accusing the army of using chemical weapons last year in its war against the RSF.

It did not provide details of where or when the alleged chemical weapons attacks took place.

Sudan's army-backed government has repeatedly denied the US allegations, calling them "baseless" and "political blackmail".

The health ministry said there were no reports of mass deaths or symptoms indicative of chemical poisoning. It said forensic pathology teams found no fatalities typically associated with chemical weapons.

The conflict that erupted between the regular army and the RSF in April 2023 has killed tens of thousands of people and driven more than 14 million from their homes, according to UN figures.

The RSF too is under US sanctions. In January, the State Department determined that the group had "committed genocide" against some ethnic groups in the western region of Darfur and imposed sanctions on its leader Mohammad Hamdan Daglo.