Visakhapatnam, July 27 - India's first nuclear submarine remains shrouded in secrecy -- despite its public launch.

The cloak of secrecy over the project, the existence of which has been denied by successive governments since its inception in 1984, was lifted Sunday when the defence ministry took journalists for the launch ceremony at this port city. However, no photography or filming of the submarine was allowed.

The official photographs of the event did not show a clear image of the submarine either.

The only glimpse of the vessel -- that has made India 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 -- was in the photograph of Prime Minister Manmohan Singh at the ceremony.

But the journalists, naval officers, 143 Russian technicians and diplomats could see the 110-metre-long and 11-metre-broad sea leviathan from the closest possible distance.

The design of the submarine that has a surface displacement of 6,000 tonnes clearly resembles the Russian Borei class nuclear-submarine. Its surface is uneven and its hull sits on a mat rolled with black square tiles, which are capable of absorbing sound waves and help it in maintaining stealth.

The white snub nose of the gleaming black submarine is the sonar (sound navigation and ranging) sheet of the vessel. It helps in recognising a vessel in the vicinity by receiving the reflected sound waves from its surface.

The conning tower is closer to the bow rather than the centre as in conventional submarines.