BRUSSELS - The European Union (EU) Monday adopted sanctions against the Russian paramilitary group Wagner, amid its concerns of the alleged Russian military build-up along the eastern Ukraine borders.

The sanctions will cover the Wagner group itself, three companies with links to the group and eight individuals, said the EU's High Representative for Foreign Affairs and Security Policy, Josep Borrell at a press conference following a meeting of the EU foreign ministers.

The listed individuals and entities will be subject to an asset freeze in the EU, and a travel ban to the EU. They will be prohibited from making funds available, either directly or indirectly, to those listed.

At Monday's press conference, Borrell reaffirmed that the bloc "stands united in support of Ukrainian sovereignty and territorial integrity," warning that any aggression by Russia against Ukraine would trigger economic sanctions that would come at a "high economic cost."

The latest measure was announced after the foreign ministers of the Group of Seven countries gathered in Liverpool from Dec 10 to 12.

During a phone call with Russian President Vladimir Putin on Monday, British Prime Minister Boris Johnson expressed concern over the alleged large-scale movement of Russian troops along the Ukrainian borders, the Kremlin said in a statement.

Putin gave Johnson specific examples of how authorities in Kiev undermined the implementation of the Minsk agreements, "which are an uncontested basis for resolving the internal crisis in Ukraine."

Putin underlined the need to immediately begin negotiations on clear and internationally legal agreements against the North Atlantic Treaty Organization's further eastward expansion and against the deployment of weapons in Russia's neighbors, primarily Ukraine.