Over the weekend, Liberal Party vice chairwoman Selina Chow Liang Shuk-yee received a letter with a five- inch razor blade attached, calling on her to "kick out" a district councillor and a dance instructor - or face the consequences.

The letter, which arrived at the offices of the Chinese-language daily Ming Pao although it was addressed to Chow, specifically named Eastern District councillor Alice Lam Chui-lin, who is a member of the Liberal Party, as well as line dance instructor Tsang Pei-kei.

Otherwise, the letter warned, someone would "slash [Chow] to death" and "blow up the Liberal Party headquarters."

The letter came just weeks after a similar set of letters arrived in the mailboxes of Chan Yuen-han, Wong Kwok-hing and Kwong Chi-kin, three lawmakers affiliated with the pro- Beijing Hong Kong Federation of Trade Unions.

All of the letters complained about Chan not having followed up on a complaint involving a district councillor in Wong Tai Sin.

The common thread tying the four letters together is the warnings about district councillors and dance instructors, and the sender - who identified herself as "Auntie Number Seven."

But for all their provocation, the letters don't seem to have scared anybody.

The letter to Chow was one page long and written in a childish red scrawl. Ming Pao said that a similar letter was also sent to Liberal Party headquarters.

A police spokeswoman said that the force received two reports of threatening letters Monday afternoon, and are treating the case as one of "criminal intimidation."

The case is still under investigation, she said, refusing to provide any details.

Chow did not respond to an interview request Tuesday, but Ming Pao quoted her as shrugging off the "strange" letter as an occupational hazard of being in public office.

Lam, meanwhile, said she made a report to police in October after receiving a similar threat but that she is not concerned for her personal safety.

Tsang, the dance instructor, said she had taught classes in both of those districts - Wong Tai Sin and Eastern District - and wondered if the letters are related to her popularity among middle-aged Hong Kong women.

She, too, was unshaken by the news.

Kwong said that there has been no developments since the first three letters, but said the letter to Chow raises the possibility a serial letter-writer may be involved.

"It seems like they were done by the same person," he said, adding that the letter to Chan also makes references to her inaction in reinstituting the death penalty in Hong Kong.

"She said she was going to kill Chan Yuen-han - that was quite ridiculous," Kwong said.

This recent wave of letters does stand out in another respect: last year, a string of razor-blade letters was sent to pro-democracy lawmakers.

This year, it seems, the targets are all pro-Beijing figures.