Russian President Vladimir Putin warned on Tuesday of "serious consequences" if Western countries allow Ukraine to use its weapons to attack Russia.

Speaking in Uzbekistan, Putin spoke in response to calls from some NATO member states to allow Ukraine to strike targets inside Russia.

"This constant escalation could lead to serious consequences," Putin said.

"In Europe, especially in smaller countries, they have to be aware of what they are playing with," he added.

The Russian leader said leaders should take into account the "small territory" and "dense population" of many European countries.

“And this is a factor that they should take into account before talking about striking deep into Russian territory, and that is a serious thing.”

He said that although Ukraine would carry out strikes, responsibility for them would lie with Western arms suppliers.

"They want a global conflict," he added.

Putin also said that while he believed Western military trainers were already in Ukraine, operating undercover as mercenaries, officially sending them in by countries such as France would be another "escalation."

"This is another step towards a serious conflict in Europe, towards a global conflict," he said.

Ukraine's commander-in-chief announced on Monday that talks were underway with France about sending military instructors to the country.

"There are specialists there disguised as mercenaries," Putin said, adding that "there is nothing new in this."

He said they would be "defeated" by the Russian army and that "we will do what we think is necessary, regardless of who is on the territory of Ukraine."

"They should know about this," Putin said.