EU will 'react as appropriate' to Russian nukes in Belarus

Stano said the move only further increases tensions and points to the Belarus collaboration with Russia's invasion of Ukraine.

"The European Union will of course be following very closely how this is implemented and we will be reacting as appropriate," he said.

Similar statements were made last March by the EU's foreign policy chief, Josep Borrell, after Russia and Belarus had announced the plans.

Borrell, in a tweet at the time, threatened to impose further EU sanctions.

The two sides had signed an agreement on Thursday to formalise the plan to place Russian tactical nuclear missiles on Belarusian territory.

TASS news agency quoted Russian defence minister Sergei Shoigu as saying the deployment was necessary "in the context of an extremely sharp escalation of threats on the western borders of Russia and Belarus."

Shoigu said that Moscow will retain control over the nukes and any decisions on their use.

In April, Shoigu also reportedly said that Russia had delivered to Belarus attack aircraft and Iskander-M systems capable of delivering tactical nuclear strikes.

Belarus shares borders with EU member states Lithuania, Latvia and Poland.

All are also members of Nato, the intergovernmental military alliance set up post-WWII to deter Soviet expansion into Europe.

Russia's president Vladimir Putin, who is wanted by the International Criminal Court for alleged war crimes, has in the past brandished the threat of nuclear war.

The country has an estimated 2,000 tactical nuclear weapons.