BRUSSELS, June 27 (Aljazeera) - NATO Secretary-General Jens Stoltenberg has said the Western military alliance is ready to defend itself against any threat posed by the move of Russia’s Wagner mercenary force to Belarus amid fears the relocation of the private army could create instability for NATO’s Eastern European members.

Wagner boss Yevgeny Prigozhin was reported to have arrived in Belarus on Tuesday under a deal negotiated by Belarusian President Alexander Lukashenko, which narrowly prevented the mercenaries from marching on Moscow on Saturday after the private army mutinied against Russia’s military leaders.

“If Wagner deploys its serial killers in Belarus, all neighbouring countries face even bigger danger of instability,” Lithuanian President Gitanas Nauseda said after a meeting in The Hague with NATO’s Stoltenberg and government leaders from six other NATO allies.

Polish President Andrzej Duda said he hoped the threat posed by Wagner mercenaries to NATO would be on the agenda at a summit of all 31 members in Vilnius, Lithuania, on July 11-12.

“This is really serious and very concerning, and we have to make very strong decisions. It requires a very, very tough answer of NATO,” Duda said.

NATO’s Stoltenberg said it was too early to say what the Wagner presence in Belarus could mean for NATO allies, but that the military alliance would protect “every ally, every inch of NATO territory” against threats from either “Moscow or Minsk”.

“We have already increased our military presence in the eastern part of the alliance and we will make further decisions to further strengthen our collective defence with more high-readiness forces and more capabilities at the upcoming summit,” Stoltenberg said.

Prigozhin has not been seen since Saturday, when he waved to well-wishers from a vehicle in the southern Russian city of Rostov-on-Don, which his fighters briefly occupied.

On Tuesday morning, a private jet believed to belong to Prigozhin flew from Rostov to an airbase southwest of the Belarusian capital of Minsk, according to data from FlightRadar24.