Belarus said on Tuesday that there was a significant grouping of Ukrainian troops massed near its border and warned that this posed a threat to its security.
"At present, a significant grouping of the Ukrainian army is concentrated in the immediate vicinity of the Belarusian-Ukrainian section of the state border," the defence ministry said in a post on Telegram.
"The probability of armed provocations, which can escalate into border incidents, has been high for a long time," it said, adding that it would take "measures to adequately respond" but would act in a restrained way.
Reuters was unable to immediately verify the situation at the border.
Belarus allowed Russia to use its territory as a launchpad for the invasion of Ukraine a year ago, and President Alexander Lukashenko said last week it was ready to do so again.
Kyiv has voiced concerns for months that Belarus could join the war on Russia's side, a potential threat that has forced it to divert troops to defend the north of Ukraine while waging war with Russia in the east and south.
Lukashenko says Belarus would only enter the war if attacked by Ukraine.
His army has been training with Russian forces for months. Tuesday's statement said more than 150 joint events were planned this year, including a major exercise called "Union Shield 2023" in September.
(Reporting by Reuters; writing by Caleb Davis and Mark TrevelyanEditing by Gareth Jones)
