According to South Stream Transport executive director Oleg Aksyutin, these contracts will cover the remaining two subsea lines in the Black Sea.

Contracts to install the first two subsea lines have already been awarded. Italy’s Saipem is due to start laying the first pipeline from Russia to Bulgaria during the first half of 2015.

Installation of the second line is expected to begin immediately afterwards by Switzerland-registered Allseas, which will use its new pipelay vessel, Pieter Schelte, for the job.

The offshore section of South Stream will consist of four parallel lines, each 931 kilometres long, with a combined annual capacity of 63 billion cubic metres of gas.

Gazprom, the major South Stream shareholder, still expects first gas to flow into the system in 2016 despite objections to the pipeline project by the European Commission.

Moscow-based analysts said that the conflict in Ukraine, which is responsible for the transit of the bulk of Russian gas to Europe, has increased the importance to Gazprom of South Stream, Against the background of this conflict, analysts said South Stream Transport’s minority shareholder, Italy’s Eni, has won major concessions from Gazprom.

Under a revised long-term gas supply deal between Eni and Gazprom, the gas giant has abandoned its 50-year old system of indexing its gas supplies to a basket of oil and products prices.

Instead, the revised agreement, backdated to 1 January this year, sees “an important change” in the price-indexation mechanism to fully align contracts with the spot market, said Eni.

Eni has a 20% stake in South Stream Transport and is expected to be a major buyer of Russian gas destined for north Italy, where the export pipeline will terminate.