Poland said on Tuesday it was rushing troops to its eastern border after accusing Belarus, Russia's closest ally, of violating its airspace with military helicopters.
The Belarusian military denied any such violation and accused NATO member Poland, one of Ukraine's most fervent backers in its conflict with Russia, of making up the accusation to justify a buildup of its troops.
Belarus leader Alexander Lukashenko had earlier taunted Poland over the presence of Russian Wagner mercenaries near their joint border.
Poland's Defence Ministry said it was sending "additional forces and resources, including combat helicopters". It said it had informed NATO of the border violation and Belarus' charge d'affaires had been summoned to provide an explanation.
The Polish military initially denied any border violation had occurred but later, after consultations, said the intrusion took place "at a very low height, hard to intercept by radar".
Belarus' defence ministry, writing on Telegram, said Warsaw had changed its mind about the incident "apparently after consulting its overseas masters".
"This statement was not backed up by data from Poland," it said. "The Belarusian Defence Ministry views it in the manner of an 'old wives' tale' and notes there were no border violations by Mi-8 and Mi-24 helicopters."
Residents of areas near the eastern Polish city of Bialowieza, close to the Belarus border, shared accounts on social media of what they said were border violations before the defence minister issued its statement.
HISTORY OF ANIMOSITY
Belarus has allowed Russian President Vladimir Putin to use its territory as a launch pad for the Ukraine invasion, but Lukashenko has not committed his own troops to the war.
The ex-Soviet state has a long history of animosity with Poland, as does Russia.
Last week, Putin accused Poland of harbouring territorial ambitions on Belarus and said it would consider any attack on its neighbour as an attack on itself.
Earlier on Tuesday, Lukashenko mockingly told Poland it should thank him for keeping in check Wagner mercenaries now stationed in Belarus after an abortive mutiny against the Kremlin last month.
An unspecified number of the Wagner fighters have since moved to Belarus and begun training Lukashenko's army. Poland had already started moving more than 1,000 of its own troops closer to the border.
Lukashenko joked at a meeting with Putin last month that some of the fighters were keen to press into Poland and "go on a trip to Warsaw and Rzeszow".
State news agency Belta quoted him on Tuesday as saying that the Poles "should pray that we're holding onto (the Wagner fighters) and providing for them. Otherwise, without us, they would have seeped through and smashed up Rzeszow and Warsaw in no small way. So they shouldn't reproach me, they should say thank you."
Rzeszow is a city near the Ukrainian border.
On Saturday, Polish Prime Minister Mateusz Morawiecki said a group of 100 Wagner fighters had moved closer to the Belarusian city of Grodno near the Polish border, describing the situation as "increasingly dangerous".
REUTERS