Updated 1.30pm

Italy's Navy on Thursday warned that a bigger Russian presence in the Mediterranean was increasing tensions and risked a possible "incident", Italian news agencies reported.

Navy Chief of Staff Enrico Credendino told the parliamentary defence commission there was a "striking increase of ships of the Russian fleet in the Mediterranean," not seen even during the Cold War, according to news agencies AGI and ANSA.

The rise in numbers "is not a direct threat to national territory, but it increases tension," Credendino said. 

"The risk of an incident is possible and when one occurs, you don't know where it may end," he added.

Credendino said Russia had 15 ships and three submarines in the Mediterranean "until a few weeks ago".

"The Mediterranean sea is a very turbulent area, with continuous competition between coastal states for access to economic resources and is the scene of illicit activities of various kinds, including smuggling and human trafficking," he said. 

"It needs to be constantly monitored."

The Mediterranean is strategically important to Europe and NATO. Some 65 per cent of the EU's energy supply and 30 per cent of global commerce crosses the sea.