Kyiv said Thursday increasingly hostile statements from Belarus and Russia and the deployment of a joint force signalled a "growing" threats of an offensive launched by Moscow from Belarus, north of Ukraine.
This comes after the creation of the new force between Minsk and Moscow, tasked with defending the Belarusian borders, was announced last week.
"The aggressive rhetoric of the military-political leadership of Russia and Belarus is intensifying," Deputy Chief of the Ukrainian General Staff Oleksiy Gromov said during a briefing.
"The threat of the resumption of the offensive by the Russian armed forces on the northern front is growing," Gromov said.
An offensive could be launched "to the west of the Belarusian border, to cut the main logistical arteries for the supply of weapons and military equipment to Ukraine" from countries west of Ukraine, including from Poland.
Earlier on Thursday Belarusian security services (KGB) said "almost every day we see increasing intelligence activities from the Ukrainian territory and attempts to violate the Belarusian airspace" in a statement quoted by state-run agency Belta.
On Monday, Minsk said up to 9,000 Russian soldiers and around 170 tanks would be deployed to Belarus as part of the task joint force.
Belarus says the force will be uniquely defensive and aims to secure its borders.
But Ukrainian President Volodymyr Zelensky accused Russia of "trying to directly draw Belarus into this war" at a recent G7 meeting.
