India’s Prime Minister Narendra Modi has opened the country’s first partially underwater metro line during a trip to Kolkata to inaugurate a number of new lines.

The underwater metro is part of Howrah Maidan to Esplanade metro in Kolkata and goes under the Hooghly river, connecting the twin cities with a 520m tunnel.

Modi described it as a “proud moment” to ride the through the underwater tunnel, saying: “It’s a very special day for the people of Kolkata as the city’s metro network gets significantly enhanced. Connectivity will get a boost and traffic will get decongested.”

In addition to the Howrah to Kolkata connection, Modi also inaugurated the Kavi Subhash to Hemanta Mukhopadhyay and the Taratala to Majerhat sections of the Kolkata metro, a new stretch of the Pune Metro, and a stretch of the Agra Metro.

The Prime Minister also opened the Kochi Metro Phase I extension project and the Duhai to Modinagar (North) section of the Delhi to Meerut Regional Rapid Transit System (RRTS) Corridor, flagging off trains along the routes.

Modi’s visit to Kolkata is part of a continued focus on expanding India’s rail infrastructure, with metro services now in operation in 15 cities in the country.

The visit comes not long after the PM flagged off the first RRTS service in October, with the first RAPIDX train on the Sahibabad to Duhai section of the $4bn project, which now runs between the country’s capital Delhi and Meerut.