New Delhi: As the country debates on death mystery of Netaji Subhas Chandra Bose, former prime minister Lal Bahadur Shastri's son Anil Shastri, Saturday, urged the central government to declassify the files related to his father's death.

While urging the NDA government to order a probe into Shastri's death, Anil Shastri, a member of Congress, told news agency ANI that many people think his father's death was not natural as his body had turned blue and a diary was also missing from the room of a Russia hotel in which the former PM was staying.

Accusing the then Indian embassy in Russia of being careless, Lal Bahadur Shastri's son said his father's hotel room in Tashkent did not even had a bell or a telephone.

In an interview to CNN-IBN, Anil Shastri said his mother had also believed that her husband didn't die a natural death.

The Congress member also questioned as to why didn't the Indian administration requested former Soviet Union to conduct port-mortem of his father's body.

Anil Shastri appealed to Prime Minister Narendra Modi to declassify all files related to the death of the former PM to clear the air around the circumstances of his demise.

The former PM had died under suspicious circumstances in Russia in 1966 where he had signed a peace pact with Pakistan a few hours earlier.

The UPA government had rejected RTI application demanding declassifying the files related to Shastri, saying that doing so would hamper foreign relations.

Shastri's family have appealed to the previous Manmohan Singh government thrice, but nothing was done.

Lal Bahadur Shastri died in Tashkent on January 11, 1966 at the age of 61 soon after signing the Tashkent Pact with Pakistan. It was maintained that Shastri had died of cardiac arrest but his family had alleged foul play.

The demand to declassify files on Shastri comes after West Bengal government last week released the top secret files related to Netaji.