NATO member states have called on Russia to immediately stop the escalation, end its practice of aggressive provocations and respect its international obligations, NATO Secretary General Jens Stoltenberg said.

"The allies fully support Ukraine's sovereignty and territorial integrity, and we call on Russia to immediately ease tensions, end its practice of aggressive provocations and respect its international obligations," he said at a press conference in Brussels on Wednesday following a videoconference of the North Atlantic Council with the participation of foreign ministers NATO countries and defense ministers.

Stoltenberg said that NATO ministers have considered building up Russia's military presence in and around Ukraine.

The secretary general also said this is the largest build-up of Russian troops since the illegal annexation of Crimea in 2014, and it is part of a broader trend of aggressive Russian actions that are causing very serious concern.