Russia's defense ministry says two of its navy destroyers forced away a Dutch submarine to stop it spying on an aircraft carrier in the Mediterranean, BBC News reports.

The sub was 20km (12 miles) from the Admiral Kuznetsov at the time of the incident, the military said.

Russia sent a flotilla to the eastern Mediterranean ahead of an expected resumption of air strikes in Syria.

Nato said it was monitoring the ships in a "measured and responsible way".

An official said the Western military alliance would not go into details but said it had been observing the fleet for some weeks.

The Russian flotilla's conspicuous voyage from Severomorsk in northern Russia, through the North Sea and the English Channel and into the Mediterranean, has rung alarm bells among Nato allies.