"Today is historic because it marks the completing of the successful establishment of the nuclear triad. India's nuclear triad will be an important pillar of global peace and stability," said Modi on Twitter.
Named INS Arihant, the submarine, which according to NDTV can target China, had been thirty years in the making and can "now be considered a fully functional underwater ballistic missile delivery platform".
"In an era such as this, a credible nuclear deterrence is the need of the hour," said the Indian premier. "The success of INS Arihant gives a fitting response to those who indulge in nuclear blackmail."
The newly launched submarine, NDTV adds, "completes India's nuclear triad by adding maritime strike capability to land and air-based delivery platforms" -- a feat Pakistan had already achieved in 2017 with the launch of Babur-3 missile.
In March this year, Pakistan carried out another successful test of the nuclear-capable Submarine Launched Cruise Missile (SLCM) Babur and announced that it has attained 'Credible Second Strike Capability'.