A senior ally of President Vladimir Putin warned on Thursday that any Ukrainian attacks on missile launch sites inside Russia with arms supplied by the United States and its allies would risk a nuclear response from Moscow, Paralel.Az reports citing Reuters.

Former Russian President Dmitry Medvedev, now deputy chairman of Russia's Security Council, said that some Ukrainian military commanders were considering hitting missile launch sites inside Russia with Western-supplied long-range missiles.

He did not name the commanders or disclose more details of the alleged plan and there was no immediate reaction from Ukraine to his threat.

"What does this mean? It means only one thing – they risk running into the action of paragraph 19 of the fundamentals of Russia's state policy in the field of nuclear deterrence," Medvedev wrote on the Telegram messaging app.

"This should be remembered," Medvedev said.

Paragraph nineteen of Russia's 2020 nuclear doctrine sets out the conditions under which a Russian president would consider using a nuclear weapon: broadly as a response to an attack using nuclear or other weapons of mass destruction, or to the use of conventional weapons against Russia "when the very existence of the state is put under threat."

Medvedev made specific mention of point "g" of paragraph nineteen which deals with the nuclear response to a conventional weapons attack.