Russia and Belarus have started 10 days of joint military drills amid ongoing fears of a Russian invasion of Ukraine.
Belarus is a close ally of Russia and has a long border with Ukraine.
France called the drills - believed to be Russia's biggest deployment to Belarus since the Cold War - a "violent gesture". Ukraine says they amount to "psychological pressure".
UK Prime Minister Boris Johnson said on Thursday that Europe faces its biggest security crisis in decades.
Russia has repeatedly denied any plans to invade Ukraine despite massing more than 100,000 troops at the border.
But the US and other Western countries have warned that an attack could come at any time.