The Belarusian state border service has accused a Ukrainian military helicopter of flouting its border during drills and flying up to one kilometre (0.62 miles) into Belarusian territory, the RIA news agency reported on Saturday.
There was no immediate comment from Ukraine.
The accusation comes amid tensions in the region with Ukraine and the West accusing Russia of a military buildup that has sparked fears of a possible attack. Russia denies any such plans and accuses Ukraine of a buildup.
Belarus is a close Russian ally.
(Reporting by Tom Balmforth; editing by Matthias Williams)
