The son of the college professor H S Sabharwal, who died during student union poll violence in Ujjain, alleged some unidentified persons claiming to be Bharatiya Janata Party workers threatened on Wednesday night to kill him.

Sabharwal's son Himanshu told PTI that when he was standing in front of his house, three to four persons riding a motorcycle, claiming to be BJP workers, verbally abused him at around 2300 hours.

When he talked back, the persons threatened to kill him, Himanshu charged.

He said he had lodged a complaint with the local Neelgandha police station and sought police protection.

According to Himanshu, he was assured that a police guard would be posted in front of his house.

Earlier in the day, Himanshu filed a complaint at a local court alleging Madhya Pradesh Chief Minister Shivraj Singh Chouhan tried to influence the investigation into Prof Sabharwal's death by terming it as an accident and not a murder.

He has also sought a Central Bureau of Investigation probe into the circumstances leading to the death of his father who was a teacher in Madhav College.