British Prime Minister Boris Johnson said "despicable attacks against civilians" in Bucha and Irpin near Kyiv were evidence that Russia was committing war crimes in Ukraine.

Charlie Rowley, who was also exposed to Novichok after coming across a perfume bottle contaminated with the nerve agent last year, met Russian Ambassador Alexander Yakovenko on Saturday to ask him why Moscow had killed his girlfriend.

"Russia has embarked on a systematic effort to explore and exploit Western vulnerabilities," Gen. Mark Carleton-Smith said.