ICGB launched a tender in April for design, procurement and construction of the 182-km (113-mile) pipeline that is estimated to cost 145 million euros ($168 million). The contract winner will have 18 months to complete the project.

Other firms which have filed initial bids also includes Italy's Sicim, Greek company J&P Avax, Turkey's Fernas, a group including Sicilsaldo, Nuova Ghizzoni and Inrakat, and a consortium of Germany's Max Streicher and Greece's Terna.

ICGB will draw up a shortlist of final bidders.

Sofia plans to use the pipeline to receive one billion cubic metres (bcm) of gas per year from Azerbaijan's Shah Deniz 2 gas field after 2020, ending its almost complete reliance on Russian gas supplies.