Indian Defense Minister A.K. Antony Wednesday said that he feels sad about the sailors who lost their lives in the fire on an Indian Navy submarine in Mumbai. \"I feel sad about those navy personnel who lost their lives for the country,\" Antony told reporters outside parliament. Antony also briefed Indian Prime Minister Manmohan Singh on the incident, which was described as a major disaster of Indian navy. Indian Navy submarine INS Sindhurakshak sank Wednesday morning after it was ravaged by a massive fire preceded by a huge explosion, according to Indo-Asian News Service. At least 18 sailors were trapped onboard the vessel while some have escaped. The cause of the explosion and blaze was not immediately known, but some officials have hinted at a battery problem. The submarine was fully armed at the time of explosion.