What was the Ghazi Attack in Indian subcontinent?

Context: PNS/M Ghazi, SJ, was a Tench-class diesel-electric submarine, the first fast-attack submarine in the Pakistan Navy. She was leased from the United States Navy in 1963. 

She served in the United States Navy from 1945 to 1963 and was loaned to Pakistan under the Security Assistance Program on a four-year lease after the Ayub administration successfully negotiated with the Kennedy administration for its procurement.In 1964, she joined the Pakistan Navy and saw military action in the Indo-Pakistani theatres in the 1965 and, later in the 1971 wars.

In 1968 Ghazi executed a submerged circumnavigation of Africa and southern parts of Europe through the Indian Ocean to the Atlantic Ocean, due to the closure of the Suez Canal, in order to be refitted and updated at Gölcük, Turkey. The submarine could be armed with up to 28 Mk.14 torpedoes and had the capability of mine-laying added as part of her refit.

Starting as the only submarine in the Indo-Pakistani war of 1965, Ghazi remained the Pakistan Navy's flagship submarine until she sank under mysterious circumstances near India's eastern coast while conducting naval operations en route to the Bay of Bengal. While the Indian Navy credits Ghazi's sinking to its destroyer INS Rajput, the Pakistani military oversights and reviews stated that "the submarine sank due to either an internal explosion or accidental detonation of mines being laid by the submarine off the Visakhapatnam harbour".

In 2010 the Indian Navy destroyed all records of their investigations into this matter. Many believe this to be an attempt to falsify history.Nonetheless, Indian historians consider the sinking of Ghazi to be a notable event; as they have described the sinking as one of the "last unsolved greatest mysteries of the 1971 war."

Answer: Ghazi was a war submarine in the Pakistan Navy. The submarine was a flagship Submarine for Pakistan. It was loaned by the US Navy. In the 1971 war in the Indian Subcontinent, the Ghazi submarine sank due to various unknown circumstances. The Pakistan navy had deployed a number of underwater mines in the region. It may have been an attack by the Indian Navy and/or may have been one of the mines they had placed themselves. It's unclear what exactly happened, but the Indian Navy destroyed all records of their investigations in 2010.