Indian submarine blasts: Divers struggle to search vessel
Indian divers are struggling to search a submarine which sank after it exploded in a Mumbai dockyard with 18 sailors feared dead inside.
Rescuers are yet to reach any of the crew who were on board when two huge explosions led to a devastating fire early on Wednesday.
Officials say they have been hampered by poor visibility, restricted space and equipment displaced by the blasts.
The divers are also working to bring the vessel back to surface.
India's navy chief has warned the country to "prepare for the worst".
It is not clear what caused the blasts on the diesel and electricity-powered INS Sindhurakshak. An inquiry is under way and sabotage has not been ruled out, although officials say that looks unlikely at this stage.
Officials say divers aboard the submarine are working around the clock in difficult conditions.
The vessel is filled with sea-water and the heat of the explosion also melted parts of the internal hull, deforming the submarine hatches and preventing access to compartments.
Heavy duty pumps are being used to pump out water in order to help refloat the vessel.
As India marked Independence Day, Indian Prime Minister Manmohan Singh expressed sorrow: "We are deeply pained that we lost the submarine INS Sindurakshak in an accident yesterday. Eighteen brave sailors are feared to have lost their lives," he said.
The prime minister said it was all the more painful considering the navy's recent successes in launching a home-built submarine and acquiring a nuclear submarine.
Correspondents say that India has steadily developed its naval capabilities in recent years, motivated by its rivalry with neighbouring China, but not without setbacks.
Two huge explosions took place on board the INS Sindhurakshak after midnight on Tuesday. Firefighters spent four hours putting out the ensuing blaze.
Dramatic images on Indian television showed a large fireball illuminating the sky. Smoke from the blaze could be seen in many parts of the city. Many sailors managed to jump to safety after the blast and some were taken to hospital.
The Russian-built vessel had recently been upgraded at a cost of $80m (£52m) and it may have been armed with missiles and torpedoes.
Russian firm Zvyozdochka, which refitted the submarine, said the vessel had been fully operational when it was returned to India in January.
On Wednesday Indian Defence Minister AK Antony visited the site. Describing the events as a "shocking tragedy", he offered his condolences to relatives of those who may have perished.
The INS Sindhurakshak is one of the 10 Kilo-class submarines bought from Russia between 1986 and 2000. It is equipped with Russian Club-S cruise missile systems.
The submarine was sent to Russia for the refit in 2010 after a sailor on board was killed by a fire that broke out in the battery compartment while the submarine was docked at the Vishakhapatnam naval base in February that year.
Wednesday's explosions came two days after India's navy launched its first home-built aircraft carrier, hailed by defence officials as a "crowning glory".
Although India can point to growing naval ambitions, correspondents say the country's military has encountered numerous scandals and difficulties.
On Tuesday India's federal auditor suggested that the government might have paid too much for 12 helicopters from Anglo-Italian company Agusta Westland, saying procurement procedures designed to ensure value for money were not properly followed.
Last year, India bought a Russian Nerpa nuclear submarine for its navy on a 10-year lease from Russia at the cost of nearly $1bn, making it part of a small group of nations to operate nuclear-powered submarines.
India and Russia are long-time allies and Russia supplies about 70% of India's military hardware.