Russia said Wednesday that sending NATO troops into Ukraine would potentially be extremely dangerous, and Moscow was closely watching a Ukrainian petition that called for such an intervention.

The petition, posted on the Ukrainian president's website, says Ukraine should ask the United States, Britain and other countries to send troops to help it repel Russia's invasion.

"The Kyiv regime is quite unpredictable," Kremlin spokesman Dmitry Peskov said when asked about it at his daily briefing.

"We have repeatedly said that direct intervention on the ground in this conflict by the military of NATO countries potentially carries enormous danger, so we consider this an extremely challenging provocation, nothing less, and, of course, we are watching this very carefully."

It was unclear if the petition would gather the required number of votes – 25,000 – to require President Volodymyr Zelenskyy to respond by either approving or rejecting it. As of Wednesday morning it had attracted 1,594 votes.

NATO has backed Ukraine in the war by providing it with increasingly powerful weapons including tanks and long-range missiles, but has not intervened directly with troops –  something President Joe Biden and Russian President Vladimir Putin have both warned could lead to World War III.

French President Emmanuel Macron has said the question of sending Western troops to Ukraine would "legitimately" arise if Russia broke through Ukrainian lines and Kyiv requested it.

Russian Foreign Ministry spokeswoman Maria Zakharova said Wednesday that Russia would target French troops if they were sent to Ukraine.

Russia warned France on Wednesday that if President Emmanuel Macron sent troops to Ukraine then they would be seen as legitimate targets by the Russian military.

Macron caused controversy in February by saying he could not rule out the deployment of ground troops in Ukraine in the future. The French leader warned that if Russia wins in Ukraine then Europe's credibility will be reduced to zero.

"It is characteristic that Macron himself explains this rhetoric with the desire to create some kind of 'strategic uncertainty' for Russia," Russian Foreign Ministry Spokeswoman Maria Zakharova told reporters.

"We have to disappoint him – for us the situation looks more than certain," Zakharova said.

"If the French appear in the conflict zone, they will inevitably become targets for the Russian armed forces. It seems to me that Paris already has proof of this."

Zakharova said Russia was already seeing growing numbers of French nationals among those killed in Ukraine.

Russia said Monday it would practice the deployment of tactical nuclear weapons as part of a military exercise after what the Moscow said were threats from France, Britain and the United States.