New Delhi: In a major boost to indigenisation of defence manufacturing, India's first nuclear-powered and nuclear-armed submarine INS Arihant was on Monday flagged off by the Defence Minister Manohar Parrikar from Vizag for sea trials.

According to the Naval sources, INS Arihant kick-started its maiden sea trial from the Shipbuilding Centre, Visakhapatnam today. Huge preparations were done to ensure a smooth sail out for the 6,000-tonne nuclear powered ballistic missile submarine (SSBN).

Arihant's sea trial will include the firing of the indigenous Bo5 missile that has a 700-km range and can carry a one tonne nuclear warhead. It can carry 12 such missiles.

Construction of INS Arihant is considered to be a giant stride of India to secure a seaborne nuclear deterrent.

The nuclear submarine will help India achieve the capability of going into high seas without the need to surface the vessel for long durations.

Conventional diesel-electric submarines have to come up on surface at regular intervals for charging the cells of the vessel.

India is the only nation in the Indian Ocean region to have a nuclear submarine and the sixth in the world to have the capability to design and construct a nuclear submarine.

Once the trials are through and the submarine enters service, India will not only complete its nuclear triad of delivering nuclear weapons from land, sea and air, but also join an elite club of six nations that operate nuclear submarines carrying ballistic missiles. The US, Russia, France, Britain and China are the other nations with this capability.

INS Arihant is longer than any of the submarine in the Indian Navy`s fleet so far. A nuclear submarine is powered by a nuclear reactor, which generates tremendous heat driving a steam turbine. It has unlimited underwater endurance and speed twice that of its conventional counterparts.

The INS Arihant's miniaturised nuclear reactor, built with Russian help, had gone critical last year and the vessel has been going through a series of harbour trials since then at Visakhapatnam, where it is being built.

The submarine has also been going through the power-up cycle of its nuclear reactor and has now achieved a nearly 100 percent power level, as per officials.

The vessel, the lead ship of the Arihant-class submarines, was launched in 2009. Its design is based on the Russian Akula-1 class submarines and its 83MW pressurised heavy water reactor has been built with significant Russian assistance.

While its 100-member crew has been trained by Russian specialists, Indian scientists at Mumbai's Bhabha Atomic Research Centre have received significant expertise in reducing the size of the reactor to help it fit into the 10 metre diameter hull of the submarine.

The Indian Navy currently operates the INS Chakra nuclear-powered submarine leased for 10 years from Russia in 2012.

Two other vessels of the Arihant class are also believed to be under construction at Visakhapatnam's state-owned Hindustan Shipyard Limited.

(With Agency inputs)