"We know what does it mean for Belarus to be nuclear. It means that Russia will put nuclear weapons in Belarus and this is a very dangerous path," EU foreign policy chief Josep Borrell said.

The move by Belarus comes as the country is being condemned internationally for being used as a launchpad by Russian forces to attack neighbouring Ukraine.

Borrell slammed the "fake referendum" Sunday where constitutional changes were approved that now allow the country to host nuclear weapons and Russian forces permanently, and extended the rule of leader Alexander Lukashenko.

Lukashenko has launched a ferocious crackdown on opponents since mass protests erupted after he claimed victory at an election in 2020 called fraudulent by the West.

The Belarusian leader, who has been in power since 1994, has shifted decisively towards Moscow after Russian President Vladimir Putin helped prop up his rule.

The EU is set to impose a new raft of tough sanctions on Belarus as Minsk has facilitated Moscow's invasion of by acting as a staging post for forces involved in the assault.

Western allies fear the constitutional shift from Belarus -- which neighbours three EU and NATO countries -- could now bring more Russian nuclear weapons closer to their border.

Russia has the world's largest arsenal of nuclear weapons and a huge cache of ballistic missiles.

Putin on Sunday ordered his nuclear forces on high alert in a move the West said was "totally unacceptable".