It comes after NATO allies allowed Ukraine to use similar arms to strike targets deep within Russian territory.
ADVERTISEMENTRussian President Vladimir Putin warned on Wednesday that Russia could provide long-range weapons to others to strike Western targets.
He also reaffirmed Moscow’s readiness to use nuclear weapons if it sees a threat to its sovereignty.
The move comes after Germany recently joined the US in authorising Ukraine to hit some targets on Russian soil with the long-range weapons they are supplying to Kyiv.
Putin said Kyiv using such weapons would be a “dangerous step”, which could also ruin relations between Berlin and Moscow.
Such action by the West will further undermine international security and could lead to “very serious problems.” he said, adding that the Kremlin could provide long-range weapons to others to strike Western targets.
“That would mark their direct involvement in the war against the Russian Federation, and we reserve the right to act the same way”.
Putin took questions from international journalists — something that has become extremely rare since Moscow sent troops into Ukraine.
'Nothing will change' after US presidential vote
On Wednesday, a Western official and a US senator said Ukraine had used US weapons to strike inside Russia under newly approved guidance from President Joe Biden.
It allows US arms to be used for the limited purpose of defending Kharkiv, Ukraine’s second-largest city. The official was not authorised to comment publicly on the sensitive matter and spoke on condition of anonymity.
Taking questions from international journalists for the first time since his inauguration last month to a fifth term, Putin also said nothing will change in terms of Russia-US relations regardless of whether Biden or Donald Trump wins the US presidential election in November.
“We will work with any president the American people elect,” Putin said, speaking on the sidelines of the St Petersburg International Economic Forum.
“I say absolutely sincerely, I wouldn’t say that we believe that after the election something will change on the Russian track in the American politics,” he added. “We don’t think so. We think nothing that serious will happen.”
Putin also said Trump’s felony conviction at his hush money trial last week was the result of "the use of the court system as part of the internal political struggle.”
Asked about Russian military losses, Putin said that no country would reveal that information during hostilities but claimed without providing details that Ukraine's casualties are five times greater than Russia’s.
He also said Ukraine has more than 1,300 Moscow troops in captivity, while more than 6,400 Ukrainian soldiers are being held in Russia.
The claims could not be independently verified.