Thiruvananthapuram, March 19 (IANS): Congress leaders should answer why no complaint has been registered against union minister Shashi Tharoor in connection with his wife Sunanda Pushkar's mysterious death, CPI-M leader V.S. Achutanandan said Wednesday.

"It's time that Defence Minister A.K. Antony and other senior leaders in the Congress break their silence on the mysterious death of Tharoor's wife," Achutanandan said in a written statement issued here.

Pushkar was found dead in her room at a five-star hotel in Delhi in January. The death triggered a controversy in the media especially because of reports of differences between Pushkar and Tharoor.

Achutanandan said that as per law, if a woman dies an unnatural death within seven years of her marriage, a case should be registered against her husband.

"Their marriage lasted under three years and hospital authorities and police have already gone on record stating that her death was a mystery. Till now, no case has been registered against Tharoor and the silence of Antony and the central government is baffling," he said.

Achuthanandan's statement came after a complaint filed by Tharoor Tuesday with poll officials over the slander unleashed against him by M. Vijayakumar, former Kerala assembly speaker and a senior leader of the Communist Party of India-Marxist and also a close aide of Achuthanandan.

At an election meeting, Vijaykumar reportedly said Tharoor could be given a doctorate in "violence against women".

Following Tharoor's complaint, poll authorities have now asked the CPI-M leader to respond to the charge.

Tharoor Tuesday also filed his nomination papers as the Congress candidate from the Thiruvananthapuram Lok Sabha seat, which he won in the 2009 polls.