The EU has slammed an agreement to let Russia deploy nuclear weapons in Belarus.

EU foreign policy chief Josep Borrell said in a statement that this was a “very dangerous escalation” that violated several international treaties.

Russia proceeded on Thursday with its plan to station tactical nuclear warheads in Belarus, which its leader said were already moving. Russian President Vladimir Putin announced the plan in March.

On Thursday, Russian Defence Minister Sergei Shoigu said he was signing papers in Minsk on how to store the weapons in Belarus.

Borrell said the decision was part of Russia’s “illegal and unprovoked war of aggression against Ukraine” and that Belarus was an accomplice.

“We urge Belarusian authorities to stop supporting Russia’s war of aggression against Ukraine, and undo decisions that only increase tensions in the region and undermine Belarus’ sovereignty,” Borrell said.

He said any further attempt “to escalate the situation will face a strong and coordinated response”.