Congratulating the crew of Strategic Strike Nuclear Submarine (SSBN) INS Arihant, Prime Minister Narendra Modi said India's new capability was a "fitting response to those who indulge in nuclear blackmail".
"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," Modi tweeted.
"The success of INS Arihant enhances India's security needs. It is a major achievement for our entire nation. In an era such as this, a credible nuclear deterrence is the need of the hour.
He said the successful completion of its deterrence patrol "gives a fitting response to those who indulge in nuclear blackmail".
He said INS Arihant will "contribute" to the atmosphere of peace in the region.
"India is a land of peace. Values of togetherness are enshrined in our culture. Peace is our strength, not our weakness. Our nuclear programme must be seen with regard to India's efforts to further world peace and stability," Modi said.
The 6,000 tonne Arihant was built under the Advanced Technology Vessel (ATV) project at the Ship Building Centre at Visakhapatnam.
Launched on July 26, 2009 by then Prime Minister Manmohan Singh, the submarine was commissioned in August 2016 after a series of extensive sea trials.