After refusing to provide Ukraine with weapons as it faces the prospect of a Russian invasion, Germany offered on Wednesday to send 5,000 helmets to the country instead, a proposal the mayor of Kyiv slammed as an "absolute joke."

German Justice Minister Christine Lambrecht said the planned delivery would send a "very clear signal" that Germany stands by Ukraine amid rising tensions with Russia.

But Kyiv Mayor Vitali Klitschko said the helmet offer had left him "speechless."

He accused Germany of failing to understand "that we are dealing with a highly equipped Russian army that could start further invading Ukraine at any moment."

"Five thousand helmets are an absolute joke," he told the Bild daily. "What will Germany send next? Pillows?"

The move was also slammed in Germany, with a meme circulating on social media using an image from a 2019 campaign encouraging young people to wear cycling helmets, with the slogan: "Looks like s**t. But saves my life."

With tens of thousands of Russian troops gathered on the Ukrainian border, fears are mounting that a major conflict could break out in Europe.

Ukraine's calls to Western allies to bolster its defense capabilities have seen the United States, Britain and Baltic states agree to send to Kyiv weapons, including anti-tank and anti-aircraft missiles.

But Germany has refused to supply Ukraine with weapons, claiming this would further inflame the conflict.

Defense Minister Lambrecht said earlier this week that Germany would deliver a field hospital to Ukraine, and that Berlin has already provided respirators.

But Ukraine's Foreign Minister Dmytro Kuleba has condemned Germany for its refusal to supply armaments to Kyiv, urging Berlin to stop "undermining unity" and "encouraging Vladimir Putin."