The sons of two Russian politicians sanctioned by the EU over the Ukraine crisis are carrying out their business activity in Bulgaria, according to the daily Trud.

Alexey Kozak, whose father is Russian Deputy Prime Minister Dmitry Kozak, and Russian Parliament Legal Committee Chairman Vladimir Pligin's son Aleksander both own enterprises based in the Black Sea city of Varna.

Russia's daily Vedomosti has also revealed that Vladimir Pligin's wife Nina has an apartment in Bulgaria with a surface of 171 square meters and a 0.5-daa plot, even though the property register does not provide such information.

The EU's earlier decision to impose sanctions on Russian officials allegedly responsible for Moscow actions on the Ukraine crisis implies the freezing of all financial assets and economic resources belonging, owned or controlled by private persons in the list.

Restrictions, however, are also targeting the assets of "private and legal persons" which are related to those blacklisted.

In Bulgaria, it is the State Agency for National Security (DANS) that is responsible for both financial intelligence and applying the sanctions.

DANS officials asked the daily Trud to submit a reference to the case so that a thorough investigation could be conducted.