US formally accuses Russia of war crimes in Ukraine

The announcement came as Joe Biden left for a trip to Europe to bolster western unity in the face of an increasingly brutal invasion. The secretary of state, Antony Blinken, said that the US had come to its conclusion using both public and intelligence sources.

She said she would support making US evidence public, whenever possible.

The US is not a party to the ICC and has opposed its investigations into crimes committed in Afghanistan and in the Palestinian occupied territories, but it has said it would help the court collect evidence on Ukraine.

The ICC prosecutor, Karim Khan, has launched an investigation into possible war crimes and crimes against humanity, and there are a range of other initiatives aimed at gathering evidence by interviewing refugees after they cross the border and through the forensic examination of the huge volume of video footage uploaded on social media.

War crimes experts have said that as the invasion has stalled, and the Russian military has resorted to increasingly desperate means and more unguided munitions, it has become more straightforward to provide evidence for war crimes cases.