The so-called Brell power grid - which stands for Belarus, Russia, Estonia, Latvia, Lithuania - is controlled almost entirely by Moscow and has long been seen as a vulnerability for the former Soviet republics, which are now Nato members.

The three Baltic states disconnected their electricity systems from Russia's power grid on Saturday, the region's operators said, part of a plan designed to integrate the countries more closely with the European Union and boost security.

Because of the Baltic decoupling, the energy system in Kaliningrad will no longer have grid connection to mainland Russia. The exclave is located between Lithuania and Poland and has not border with the rest of Russia.