The EU's foreign policy chief Josep Borrell said on Sunday that Brussels was ready to impose new sanctions on Belarus if Minsk were to host Russian nuclear weapons.

"Belarus hosting Russian nuclear weapons would mean an irresponsible escalation and threat to European security. Belarus can still stop it, it is their choice. The EU stands ready to respond with further sanctions," he tweeted.

Russian President Vladimir Putin announced Saturday his country would station tactical nuclear arms in Belarus.

Putin said the deployment was similar to moves from the United States, which stores such weapons in bases across Belgium, Germany, Italy, the Netherlands and Turkey, an analogy western allies called "misleading".

With fears of a nuclear war rising since the invasion, experts believe that any Russian strike would likely involve small-size battlefield weapons, called "tactical" as opposed to "strategic" high-powered long-range nuclear weapons.

The Ukrainian foreign ministry accused Russia of breaching its obligations, and of undermining the "nuclear disarmament architecture and the international security system in general".

It called on "all members of the international community to convey to the criminal Putin regime the categorical unacceptability of its latest nuclear provocations."

In the interview broadcast Saturday, Putin said the move to deploy tactical nuclear weapons to Belarus was "nothing unusual".