The reaction by the government spokesman comes after the United States said on Thursday it had determined that Sudan's military used chemical weapons in the country's bloody civil war last year and will impose sanctions.

"These baseless accusations are nothing but political blackmail and a deliberate falsification of the facts," Information Minister Khalid al-Aiser said in a statement, responding to sanctions announced by Washington targeting US exports to Sudan and the government's access to US credits.

The US State Department said it notified Congress on Thursday of its determination on the use of chemical weapons, triggering sanctions after 15 days.

The sanctions include restrictions on US exports and financing to Sudan's government.

In practical terms, the effect will be limited as both Sudan's military chief Abdel Fattah al-Burhan and his adversary and former deputy, Rapid Support Forces (RSF) leader Mohamed Hamdan Daglo, are already under US sanctions.

Africa's third largest country has been ravaged by more than two years of war between their respective forces.

The Sudan conflict has killed tens of thousands of people, displaced 13 million and created what the United Nations describes as the world's worst humanitarian crisis.

- 'False narrative' -

"The United States calls on the Government of Sudan to cease all chemical weapons use and uphold its obligations" under the Chemical Weapons Convention, an international treaty signed by nearly all countries that prohibits their use, the State Department said on Thursday.

The government, now based in Port Sudan, on Friday denounced the accusations that the army had engaged in chemical warfare against its rivals.

"This false narrative, which the American administration is trying to spread internationally, is just another attempt to mislead public opinion," Aiser said.

He accused Washington of "complicity" with the RSF, citing in particular "the support of the United Arab Emirates".

The UAE has always rejected the charge that it supplies weapons to the RSF, despite numerous reports from UN experts, US political officials and international organisations.

"Washington remains silent on documented crimes against civilians in Darfur and other regions, crimes supported by the Emirates who provide militias with strategic drones and sophisticated American weapons," Aiser said.

The New York Times reported in January that Sudan's military had used chemical weapons on at least two occasions in remote areas in its war with the RSF.

Citing anonymous US officials, the newspaper said that the weapon appeared to be chlorine gas, which can cause severe respiratory pain and death.

Sudan's army said on Tuesday it had dislodged the RSF from their last positions in Omdurman, securing all of greater Khartoum nearly two months after recapturing the heart of the capital.

The war has effectively split Sudan in two, with the army holding the centre, north and east while the RSF controls nearly all of Darfur and, with its allies, parts of the south.