Along with the main branch Eysturoy Tunnel, the 10.9km Sandoyar Tunnel will connect several of the country's towns, reducing travel time by more than half. The distance between the capital, Torshavn, and the town of Strendur, for example, will be shortened from 55 to 17km.

The contract is divided into two sub-projects with a total contract value of SEK2.7 billion (US$285.87 million).

At the point of the breakthrough, witnessed by invited guests and a large number of Faroese residents, the Faroese Islands' Transport Minister Heðin Mortensen triggered an explosive charge.

The breakthrough came as planned, 27 months after NCC began the tunnel construction work in January 2017. At its deepest, the tunnel is 189m below the seabed and it boasts the Atlantic Ocean's first and only sub-sea roundabout.

"This is an important milestone in our contract on the Faroe Islands, and it showcases NCC's broad expertise in complex tunnel and infrastructure projects," said Per Jonsson, head of NCC's Civil Engineering Norway division.

"The tunnel required considerably more injection than was typical for the other tunnels on the Faroe Islands - 7,500t of injection grout, to be precise. The teams have done an excellent job. NCC has also had to battle with a zone of extremely poor rock quality," explained project manager Alf Helge Tollefsen from NCC Infrastructure.

NCC has also embarked on the second phase of the Faroese contract, building the 10.5km Sandøy Tunnel, which will run from Gamlarætt on the island of Streymoy to Traðardalur on Sandoy.