Greece, which relies on Russian gas for its energy needs, has said it expects 4 billion euros in investments by 2030 in gas pipelines, networks and storage facilities.

The third tank on the LNG terminal on Revithoussa, an islet near Athens, will increase its total storage capacity by 73 percent to 225,000 cubic metres and boost the gasification rate by 40 percent, allowing Greece to receive larger LNG cargoes.

"Revithoussa is now an advantageous hub in the southeastern Mediterranean region for natural gas," Energy Minister George Stathakis said.

Besides Russia, Greece imports LNG from Algeria, which it temporarily stores at Revithoussa before gasifying it to supply its transmission system.

Revithoussa, run by gas grid operator DESFA, is Greece's only LNG terminal. A consortium led by Italy's Snam is to buy a majority stake in DESFA by the end of the year.

Greece is developing a second LNG terminal off the northern city of Alexandroupolis that aims to supply gas to southeastern Europe via a pipeline link with Bulgaria, the Inter-connector Greece-Bulgaria (IGB).

The IGB and the LNG terminal would then connect with the Trans-Adriatic Pipeline (TAP), which has been under construction to transport Caspian gas to European markets.

Greece wants to boost the use of natural gas in electricity production, transportation and households, to cut costs and reduce its carbon footprint until it replaces most of its coal and oil-fired power plants with renewable ones by 2030.