A senior Ukrainian presidential aide said on Tuesday Belarus was stepping up "aggressive and militaristic rhetoric" ahead of the first anniversary of Russia's invasion, but that Kyiv saw no imminent threat from its northern neighbour.

The official, Mykhailo Podolyak, made the comments to Reuters after Belarus said Ukraine had massed a significant grouping of troops near their mutual border and warned of a security threat.

"We do not see any logistics action in Belarus aimed at forming a strike force. Nor do we see the accumulation of equipment needed for a ground offensive," Podolyak told Reuters.

"Official Minsk is unwaveringly supporting Russia on the information side. Nevertheless, we have the northern direction (facing Belarus) under special control." (Reporting by Pavel Polityuk; writing by Tom Balmforth; editing by Timothy Heritage)