BELARUS will respond to “aggression” with nuclear weapons, President Alexander Lukashenko warned today after its Nato-member neighbours increased security on their borders with his country.

The threat coincided with Lithuania temporarily closing two of its six border checkpoints with Belarus amid growing tensions with Russia’s close ally and concerns about the presence of Wagner Group mercenaries across the frontier.

Lithuanian State Border Guard Service commander Rustamas Liubajevas said that there could be up to 4,500 Wagner fighters in Belarus, with some of them stationed close to the Lithuanian and Polish borders.

In neighbouring Latvia, the State Border Guard Service had said on Tuesday that it was mobilising additional personnel to strengthen protection of the frontier.

Poland has been deploying tens of thousands of troops to its border with Belarus in recent days, describing this as a deterrent move.

In an interview, Mr Lukashenko said: “If aggression against our country is launched from the side of Poland, Lithuania, Latvia, we will immediately respond with everything we have.

“Nato stands behind [these countries]. We certainly understand that the forces are incomparable.

“But we will deliver an unacceptable strike against them and they will receive unacceptable harm, damage. It is what our security concept is based on.”

Mr Lukashenko added that nuclear weapons would not be used unless his country was attacked first, but if it was, then Belarus would not hesitate to launch them.

“We will use the entire arsenal of our weapons for deterrence,” he said, adding that they are a small country that can be “captured within a month.”

Both Mr Lukashenko and Russian President Vladimir Putin said in June that Belarus had received its first tactical nuclear weapons and that more would follow.