Poland is facing a "real threat" on the border with Belarus as a consequence of migration and a military exercise planned for later in September, according to a government spokesperson.

Zapad 2021, or West 2021, is a large-scale joint exercise between Russia and Belarus. It will involve thousands of military personnel carrying out exercises on Russian and Belarusian training grounds.

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Belarus's defense ministry said service personnel from Kazakhstan will also take part, along with tanks, artillery and aircraft. The ministry stated the training exercises will be based on scenarios in which "international tensions are escalated to a level that may destabilize the situation in the region and provoke aggression against the Union State [of Russia and Belarus]."

There are concerns from Poland that "something could happen"during the exercise on the nearby EU borders. Government spokesperson Piotr Muller told Polish media: "This is a way to test defense abilities of neighbouring countries". 

It's understood Belarus will be receiving a large consignment of military hardware from Russia, including helicopters and other aircraft.

Earlier in the year, Ukraine described Zapad 2021 as a threat to its own security and that of NATO. In response, Belarus's defense ministry said the exercise carried no threat, "for the European community as a whole, not for any neighboring countries."

The concerns come as Polish border guards reported 3,500 people tried to cross into Poland from Belarus in August. Polish officials say 2,500 people were stopped by guards and around 1,000 have been detained. In comparison, officials say there were no illegal crossing on the same border in August 2020.

Poland, Latvia and Lithuania have accused Belarus of driving migrants towards their borders in an attempt to destabilize the EU, with all reporting spikes in attempted crossings over the summer. Belarus has blamed the border issues on the EU and previously said migrants would not be held back.

There are currently 32 people stranded in no man's land between Poland and Belarus, as the Polish army continues to build a barbed-wire fence along the border. A group of migrants is also stuck on the Latvian border.

Poland is expected to announce a state of emergency along the border with Belarus by the end of the week to control movement in the area. A state of emergency hasn't been enforced in the country since the 1980s and would run for 30 days, affecting an area around 3km from the border, taking in 183 towns.