NEW DELHI: Indian police on Tuesday registered a murder case against unknown persons over the death of Sunanda Pushkar, claiming the wife of the Shashi Tharoor was killed by poisoning, according to a Times of India report.

"We have got the final medical report from AIIMS, and we have been told that it was an unnatural death... It was not a natural death," Delhi Police chief B S Bassi told mediapersons.

"Sunanda died due to poisoning. Whether the poison was given orally or injected into her body is being investigated," he said adding that the report from the All India Institute of Medical Sciences (AIIMS) was received on Dec 29.

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“We can only say which substance caused the poisoning after further investigation,” Bassi further said adding that, "For that we will send her viscera abroad."

Pushkar was a Dubai-based entrepreneur before she married Shashi Tharoor in 2010.

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She was found dead in a five-star hotel in New Delhi under mysterious circumstances on Jan 17 last year, a day after she had accused Pakistani journalist Mehr Tarar of “stalking” her husband and of trying to “break” her marriage when she was away for medical treatment for three months.

Tarar had denied Pushkar’s accusation of an affair between her and the former high-flying UN diplomat.