The European Union has expressed "great concern" over the movement of Russian military forces near the border with Ukraine.

Axar.az reports citing foreign media that Josep Borrell, the bloc's foreign affairs chief, also expressed "unwavering support" for Kyiv after a phone conversation with Ukraine's foreign minister Dmytro Kuleba.

"We are following with severe concern the Russian military activity surrounding Ukraine," Borrell tweeted on Sunday.

"Unwavering EU support for Ukraine's sovereignty and territorial integrity," he added.