Russian fighter jets and assault helicopters have begun training missions over the Mediterranean Sea, a Russian navy spokesman has told Interfax news agency.
Spokesman Vadim Serga revealed that the training would include tactical exercises for battle techniques and the engagement of aerial targets.
Serga said that the Northern Fleet's Admiral Kuznetsov aircraft carrier is involved in the training exercises as well as Sukhoi SU-33 air defence fighters and Kamov Ka-27 anti-submarine helicopters.
He did not mention the mounting tensions between Ukraine and Russia over the Crimea region but these exercises are thought to be in preparation for military action between the two nations.
The Crimean parliament has voted to join Russia and will put the case to voters in a referendum on 16 March. Crimeans will be asked to vote on whether the republic should join Russia or remain part of Ukraine.
The exercise comes as US Secretary of State John Kerry and Russian Foreign Minister Sergei Lavrov meet in London for last-minute talks before the Crimea referendum on Monday.
Kerry and Lavrov spoke by phone about the situation in Ukraine and Russia said the two had discussed "taking into account existing Russian and US proposals to normalise the atmosphere and provide for civil peace".
The United States has sent 12 F-16 fighter jets and 300 service personnel to Poland for a training exercise in response to the Ukraine crisis while Nato has dispatched Awacs [Airborne Warning and Control System] reconnaissance aircraft to Poland and Romania in order to monitor the Ukraine border after authorisation was granted by alliance ambassadors.
Despite the crisis, Russian President Vladimir Putin's approval ratings have reached a three-year high following the occupation of Crimea and the Sochi Winter Olympics, according to a Russian poll.