Visakhapatnam (Andhra Pradesh), July 26 - India Sunday launched its first indigenous nuclear-powered attack submarine, and Prime Minister Manmohan Singh said on the occasion that the navy had a major role to play in re-adjusting 'our military preparedness'.

Underlining that the sea was increasingly relevant in the context of India's security interests, Manmohan Singh said: 'We must re-adjust our military preparedness to this changing environment. Our navy has a huge responsibility in this regard.'

The prime minister spoke at the headquarters of the Indian Navy's Eastern Command here after his wife, Gursharan Kaur, broke a coconut and did a prayer to mark the launch of INS Arihant, a 6,000-tonne, 110-metre long and 11-metre wide submarine that can carry nearly 100 sailors.

India becomes the sixth country after the US, Russia, China, France and Britain to possess a nuclear-powered submarine.

The launch comes 25 years after the project was initiated when Indira Gandhi was the prime minister.

Calling Sunday's event a 'historic milestone', Manmohan Singh said: 'We do not have any aggressive designs nor do we seek to threaten anyone. We seek an external environment in our region, and beyond that is conducive to our peaceful development and the protection of our value systems.'

Manmohan Singh said the deep sea strategic capability was necessary in view of the increasing relevance of the sea in the country's security scenario.

The dockyard where the submarine was housed was flooded before the vessel could be tugged out. Officials said it would take two years of sea trials before the vessel is commissioned into the navy.

The submarine was built under the Advanced Technology Vessel project.