Russia said on 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 Zelenskiy 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 that U.S. President Joe Biden and Russian President Vladimir Putin have both warned could lead to World War Three.

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 on Wednesday that Russia would target French troops if they were sent to Ukraine. (Reporting by Reuters, writing by Mark Trevelyan; editing by Guy Faulconbridge)