A NEW police report has been made and university campus security roped in after Nominated MP Thio Li-ann received a threatening letter in her office mail box this week.

The anonymous writer had insinuated that 'we know where you work, we'll send people there to hunt you down', she told The Straits Times on Wednesday.

Her family was also threatened with bodily harm, the National University of Singapore law academic added as she explained what prompted her to go to the police.

Professor Thio, 39, became a lightning rod for criticism from both the gay community and others, after delivering a strongly-worded speech in Parliament last month against the repealing of Section 377A, which criminalises sex between men.

But on Wednesday, activists like Alex Au of gay interest group People Like Us were also quick to condemn the anonymous letter-writer.

Said Mr Au: 'I will totally condemn any malicious letters. It's completely against the spirit of civil discourse and democracy.'

This is the second time Prof Thio has made a police report.

She did so previously in August after playwright Alfian Sa'at sent her a four-line e-mail accusing her of 'hate-mongering' and 'vicious crusades against sexual minorities'.

He has since apologised to her.

While she regarded that incident as 'rude', this second case was 'criminal intimidation', she said.

She was aware of the letter only when she was alerted to it on Monday evening by a journalist who received a copy of it.

Prof Thio saw the letter when she checked her mailbox at the National University of Singapore's law faculty in Bukit Timah the next morning.

University campus security officers have since also briefed her on 'a safety protocol to follow', Prof Thio disclosed, without going into details.