A man watches Indian Navy submarine INS Sindhurakshak on fire in Mumbai August 13, 2013. [Photo/Agencies]

NEW DELHI - A huge explosion and fire that crippled an Indian navy submarine in its home port of Mumbai on Wednesday killed at least some of the 18 sailors aboard, the country's defense minister said.

Defense Minister A.K. Antony gave no other details but said he felt sad about the loss of lives.

"It's a loss to all of us. It's a tragedy," Antony told reporters before leaving for Mumbai to assess the situation.

Local TV news station Headlines Today showed video of the explosion on the diesel-powered submarine, apparently filmed by a bystander. An enormous ball of red and yellow fire rose hundreds of feet into the air.

One man standing outside the dockyard who declined to give his name said he heard a sound like a rocket or jet engine, then a blast. Another witness said the sky turned red after the explosion. Nearly a dozen fire engines rushed to the dockyard to douse the fire.

The fire was extinguished in about two hours, but a navy official said it was unclear how many sailors were killed or injured. The official spoke on condition of anonymity because he was not authorized to talk to reporters.

The official said that when the blast occurred, some sailors of other nearby units jumped into the sea in panic. He says some were injured and hospitalized.

Afterward, the sub was nearly submerged at its berth in the naval dockyard.

Navy spokesman Narendra Vispute said the cause of the explosion was being investigated.

The 16-year-old Russian-made submarine, INS Sindhurakshak, had recently returned from Russia after undergoing an overhaul and upgrade, said Rahul Bedi, an analyst for the independent Jane's Information Group. India has 14 diesel-powered submarines, he said.

Last year, India acquired a Russian Nerpa nuclear submarine for its navy on a 10-year lease from Russia at a cost of nearly $1 billion. India also has designed and built its own nuclear submarine; the navy activated the atomic reactor on that vessel Saturday and could deploy it in the next two years.