"Russian servicemen who are part of the (regional grouping) began to arrive in Belarus," a Belarussian defense ministry official stated.
Defense Intelligence of Ukraine said in a statement that they are seeing measures that are being taken by Russia to try and convince Belarus to join the war.
From tractors to melons to special prayers, what would you give Russian President Vladimir Putin for his birthday?
Diplomatic sources in Jerusalem were unaware of Lukashenko's presence and said they would look into it.
Iran may learn from Russia's movement of missiles to Belarus and draw conclusions about its own use of missiles in the region.
Belarus is also deploying air defense, artillery and missile units for drills in the west, Gulevich said.
Belarus, ruled by the self-declared last dictator of Europe Alexander Lukashenko, is one of Russia's closest allies.
"We didn't have a choice. It was the right decision," he said, joined by Belarusian President Lukashenko, on the 61st anniversary of the first manned space flight.
Putin and Lukashenko meet • Russian assault on Mariupol continues, at least 10,000 killed • 9 humanitarian corridors opened
According to Russian state media, Belarusian secret services thwarted a group of people planning to stage a terrorist attack at a railway station