Russia and Belarus will begin joint air force drills on Monday, which have triggered fears in Kyiv and the West that Moscow could use its ally to launch a new ground offensive in Ukraine.
Minsk says the drills are defensive, and since Moscow used its neighbour as a springboard for its invasion of Ukraine last February Belarus has conducted numerous military exercises, both on its own and jointly with Russia.
Together with Moscow, Minsk has also been bolstering the drills with weaponry and military equipment.
Unofficial Telegram military monitoring channels have been reporting a series of fighters, helicopters and military transport planes coming to Belarus since the start of the year - eight fighters and four cargo planes on Sunday alone.
Reuters was not able to verify the reports. The Belarusian defence ministry said only that "units" of Russia`s air forces have been arriving in Belarus.
"During the tactical flight exercise, all airfields and training grounds of the Air Force and Air Defence Forces of the Armed Forces of Belarus will be involved," the ministry said in a statement.
The situation on Belarus`s southern border - the border with Ukraine - was "not very calm," and Ukraine has been "provoking" Belarus, said Pavel Muraveyko, first deputy state secretary of Belarusian Security Council, according to a post on the Belarusian defence ministry`s Telegram app on Sunday.
"We`re maintaining restraint and patience, keeping our gunpowder dry," Muraveyko said. "We have the necessary set of forces and means that will respond to any manifestations of aggression or a terrorist threat on our territory."
Ukraine has continuously warned of possible attacks from Belarus and President Volodymyr Zelensky said last week that the country must be ready at its border with Belarus.
Appeal for more weapons
In his nightly address after the Dnipro strike, Zelensky called on Western allies to supply more weapons to end "Russian terror" and attacks on civilian targets.
Western powers are considering sending battle tanks to Kyiv and ahead of a meeting of Ukraine`s allies in Ramstein in Germany next Friday, where governments will announce their latest pledges of military support.
On Saturday, Britain followed France and Poland with promises of further weapons, saying it would send 14 of its Challenger 2 main battle tanks as well as other advanced artillery support in the coming weeks.
The first despatch of Western-made tanks to Ukraine is likely to be viewed by Moscow as an escalation of the conflict. The Russian Embassy in London said the tanks would drag out the confrontation.
Russia`s invasion, which Moscow calls a "special military operation", has already killed thousands, displaced millions and turned many cities into rubble.
Soledar
In Ukraine`s eastern Donbas region - the focal point of Russia`s drive to capture more territory - Ukraine`s forces were battling around the small salt-mining town of Soledar.
Russian forces claimed to have taken control of the town, but Ukraine insisted on Sunday that its forces were battling to hold the town, with street fighting raging and Russian forces advancing from various directions.
"Put simply, THE BATTLE CONTINUES," Deputy Defence Minister Hanna Maliar said on the Telegram messaging app. "Everything else is unverified information."
The Washington-based Institute for the Study of War said it was highly unlikely that Ukrainian forces still held positions within Soledar itself.
Reuters could not immediately verify the situation in the town.
