UK Prime Minister Rishi Sunak on Friday denounced a video purporting to show the beheading of a Ukrainian prisoner of war, saying those responsible should be brought to book.
Downing Street said Sunak told Ukraine’s President Volodymyr Zelensky in a call that the footage was “abhorrent”.
“The prime minister said the video was appalling and those responsible had to be held to account,” a statement read.
Russia announced on Thursday that it was opening a preliminary probe into the footage, which has sparked fury in Ukraine.
The Kremlin has vigorously denied a series of war crime allegations from Kyiv and its Western allies since Russian troops invaded Ukraine last February.
Downing Street said Sunak paid tribute to Ukrainian troops fighting to prevent Russian forces overrunning the besieged eastern city of Bakhmut.
“The leaders also discussed efforts to accelerate military support to Ukraine, and the prime minister said the UK and its allies needed to continue to ensure Ukraine was in the strongest possible position to build on its recent battlefield successes,” it added.
“That included increasing interoperability with NATO both in the short and long term.”