An alleged Belarusian helicopter incursion has prompted Poland to send 10,000 extra troops to its border with Belarus.

They say they will help guard against mercenaries from Russia’s Wagner group who have moved into Belarus and are now reportedly heading towards the border.

According to Poland’s government, two Belarus military helicopters flew into its territory about two kilometres from Bialowieza on 1 August.

At the time, the Belarusian armed forces were conducting exercises along the border.

Government officials said there were “no border violations by Mi-8 and Mi-24 helicopters”, and dismissed the allegations as “old wives’ tales”.

The residents of Bielowieza have posted photos on social media of a Mi-8 helicopter and a Mi-24 helicopter with Belarusian markings flying over their town.

According to BBC Verify, the serial numbers on the helicopters match those seen at Machulishchi airfield last year.

As a result of this military incursion, thousands of migrants have crossed illegally into Poland from Belarus.

Since 2021, Poland claims, Belarus has encouraged people from the Middle East and Africa to cross the border illegally.

Poland’s border guard says 19,000 migrants have crossed the border so far this year, and 16,000 did so last year, despite fewer crossings than two years ago.

Belarus’ strategy has been described as “hybrid warfare” by the Polish government.

A number of mercenaries from Russia’s Wagner group have moved into Belarus following their failed mutiny last June.

In a conversation with Russian President Vladimir Putin, Belarus’ leader Alexander Lukashenko joked: “They want to go to Warsaw… but I am keeping them in central Belarus.”

Mateusz Morawiecki, the Polish prime minister, said that 100 Wagner fighters had been moving toward Grodno, a city in Belarus on the Polish border, and described the situation as “increasingly dangerous”.

The Wagner fighters in Belarus could pose as migrants and enter Poland, or they could pose as Belarusian border guards and help more illegal migrants cross.

According to Belarus’ defence ministry, Wagner troops were training Belarusian troops at the Brestsky camp in the south of the country.