The US State Department on Wednesday said it had determined that both the Sudanese Armed Forces and the paramilitary Rapid Support Forces have committed war crimes in Sudan.
“Based on the State Department’s careful analysis of the law and available facts, I have determined that members of the SAF and the RSF have committed war crimes in Sudan,” Secretary of State Antony Blinken said in a statement.
“I have also determined that members of the RSF and allied militias have committed crimes against humanity and ethnic cleansing.”
Fighting broke out between the Sudanese military and the RSF on April 15 after tension over the proposed integration of the paramilitary group into the armed forces, among other issues.
Over the past eight months, thousands of people have been killed and millions displaced.
The two groups “have unleashed horrific violence, death and destruction across Sudan”, the State Department said, with civilians bearing “the brunt of this needless conflict”.
“Detainees have been abused and some killed at SAF and RSF detention sites," it said.
"Across Sudan, the RSF and allied militias have terrorised women and girls through sexual violence, attacking them in their homes, kidnapping them from the streets or targeting those trying to flee to safety across the border."
The conflict has also led to a surge in ethnic violence in places including the restive Darfur region.
The RSF and allied Arab militiamen attacked in Darfur last summer, reportedly killing hundreds or thousands of Masalit tribesmen in the town of El Geneina, forcing tens of thousands to flee across the border into Chad.
“The secretary also determined that members of the RSF and its allied militias have committed crimes against humanity as part of a widespread and systematic attack directed against Darfur's civilian population, and that members of the RSF and allied militias have also committed ethnic cleansing,” State Department spokesman Matthew Miller said on Wednesday.
The State Department urged the Sudanese military and the RSF to end the conflict, comply with international humanitarian and human rights laws, and hold those responsible for the atrocities accountable.
“It is important to send a signal to the international community about what in fact has happened here,” Mr Miller said.
“We have documented repeated atrocities, we have documented members of the factions going in and just executing civilians in villages at point-blank range.
"We've seen systematic accounts of rapes. We think it's important to point that out and call it what it is.”
Mr Miller said that the US will continue to work with partners in the region to end the conflict, making it clear there can be no military solution.
"But ultimately, that takes the two parties coming to the table and not just coming to the table, but adhering to the commitments that they make so far."
Following the announcement, Ben Cardin, chairman of the Senate Foreign Relations Committee, called on President Joe Biden to appoint a special envoy on Sudan to "co-ordinate interagency policy, help lead the efforts of our allies and partners to end the conflict, and to work with the Sudanese in support of their aspirations to establish a democratic, representative government".