Surging numbers of Wagner Group forces have prompted both Poland and Lithuania to consider shutting their borders with Belarus, government officials have confirmed.

And western nations have been warned operatives may disguise themselves as asylum seekers in order to cross into EU states.

Speaking to reporters on Friday, Arnoldas Abramavicius, Lithuania’s deputy interior minister, admitted concerns over the presence of thousands of mercenaries was a factor.

He said: “The considerations are real. The possibility of closing the border exists.”

Wagner fighters have been relocating to territory of the close Russian ally with the blessing of its President, Alexander Lukashenko, in the wake of their apparent mutiny against Russia’s military leaders.

Mr Abramavicius also claimed Wagner thugs were likely to try to conceal themselves as migrants in order to cause havoc.

He explained: “It could be some groups of refugees, irregular migrants being transferred in order to cause some kind of unrest.”

Also yesterday, Jarosław Kaczyński, chairman of Poland’s ruling Law and Justice party, said Wagner fighters were “not in Belarus for fun”.

He added: “They are there to create various types of crises, primarily directed against Poland.”

Poland had been shoring up its defences “so that these provocations, these activities, fail”, he stressed.

Both nations have both built fences along their borders with both Russia and Belarus, claiming Moscow and Minsk are purposely orchestrating influxes of migrants into the EU to foment instability.

Wagner mercenaries last week launched joint drills with the Belarusian military, with the group’s founder Yevgeny Prigozhin later vowing to help protect Belarus from a potential incursion and to bolster its military.

Poland responded by boosting troop numbers along the border.

Speaking to Express.co.uk last week, Andrii Ryzhenko, of Kyiv-based thinktank the Centre for Defence Strategies, claimed Wagner forces could use Belarus as a base from which to stage clandestine attacks on Ukraine.

He said: “The biggest risk from the Wagner Group is conducting sabotage and reconnaissance operations from the territory of Belarus.

“I believe this is possible if they find a common language there with the puppet authority of Lukashenko.”

He added: “I am not aware of the situation on the Belarusian territory, but on the northern side, facing Russia, there have been incidents where sabotage groups infiltrate and create havoc in these border areas.

“Just last week, they killed a person and seized a minibus. So, the same could happen from Belarus.”

“In conclusion, I believe that the involvement of Wagner in conducting sabotage activities on the territory of northern Ukraine is possible”.

Poland’s MPs yesterday (July 28) approved an amended but divisive law on Russian influences believed to be targeting the opposition and criticised by the US and Brussels

The law was proposed in May by Law and Justice, with and critics see it as primarily targeting opposition leader and former Prime Minister Donald Tusk, before a parliamentary election scheduled for this fall. After criticism, President Andrzej Duda proposed urgent amendments to tone it down.