Poland, Lithuania and Latvia could jointly decide to shut their borders with close Russian ally Belarus if there are serious incidents involving the Wagner group along their frontiers with the country, Poland’s Interior Minister said on Thursday.

NATO member Poland on July 19 decided to move military units to its east after Wagner mercenaries began training Belarusian special forces a few miles from its border.

Two days later President Vladimir Putin accused Poland of having territorial ambitions in the former Soviet Union, and said any aggression against Belarus would be considered an attack on Russia.

“Undoubtedly, should there be serious incidents involving the Wagner group on the borders of NATO and EU countries, such as Poland, Lithuania or Latvia, we will undoubtedly take an action together,” the minister, Mariusz Kaminski, said.

“I do not exclude that if we decide that this is the right answer at the moment, we will lead to the complete isolation of Belarus.”

Poland, which denies any territorial ambitions in Belarus, has been an important refuge for opponents of Belarus President Alexander Lukashenko, and Warsaw has become one of Kyiv’s staunchest supporters since Russia invaded Ukraine in 2022.

Road traffic between Poland and Belarus has been curbed since February amid deteriorating relations between the two countries.

Poland has also accused Belarus of artificially creating a migrant crisis on the border by flying in people from the Middle East and Africa and attempting to push them across the frontier. Belarus has repeatedly denied this.