Formal inauguration of the "Blue Stream" natural gas pipeline project started on Thursday in Turkey 's northern city of Samsun off the Black Sea, the semi-official Anatolia news agency reported.

Turkish Prime Minister Recep Tayyip Erdogan, Italian Prime Minister Silvio Berlusconi and Russian President Vladimir Putin presented at the opening ceremony of the world's deepest undersea pipeline.

To meet the gas demand of Ankara, the "Blue Stream" pipeline stretches from southern Russia under the Black Sea to the Durusu Metering Station, a natural gas terminal outside Samsun.

The full span of the pipeline is 1213 km, of which some 376 km long pipeline will be laid 2,100 meters beneath the Black Sea.

Thousands of specialists from Russia, Italy and Turkey will take part in construction of the pipeline, which is estimated to cost 3.5 billion US dollars.

Stating that "Blue Stream" project was a very important one, Paolo Scaroni, CEO of Italian State Oil Company ENI, indicated that natural gas which would be transported to Turkey could also be sold to other countries.

On Wednesday, Turkish Energy and Natural Resources Minister Hilmi Guler unveiled plans to link the "Blue Stream" pipeline to the Mediterranean port of Ceyhan to facilitate the export of natural gas and oil to third countries.

Turkey imported 1.2 billion cubic meters of natural gas from Russia in 2003 and 3.2 billion cubic meters in 2004.

As of June 2005, Turkey had imported 2.1 billion cubic meters of natural gas from Russia.

Turkey signed a contract with Russia in 1997 to receive 16 billion cubic meters of natural gas from Russia annually over the next 25 years.