The Hong Kong Police Force, long considered "Asia's finest", has confronted unprecedented hostility in recent months, with anti-government radicals regarding them as "the enemy".

Lau Chak-kei, the station sergeant of the Hong Kong Police Tactical Unit, said he never expected what would happen after he stepped in to protect a man from being roughed up by black-clad protesters. Since then, he has faced nonstop nuisance calls, torrents of verbal abuse and threats against the lives of his family members.

The 46-year-old, nicknamed "Bald-Headed Sergeant", received 700 nuisance calls in just one hour. He canceled prebooked extracurricular classes for his children in fear for their safety. The children stayed home over the summer holiday due to the fact that someone posted his personal details online.

Lau is among the 1,600-plus police officers whose personal information was posted online, placing them and their family members in potential peril. Police officers, performing their sworn duties to uphold the law, have become targets of malicious attacks by radical protesters, even though the extradition amendment legislation that set off the protests has been withdrawn.

Lau's difficulties began on July 30 when a man was attacked by a mob of radicals in Kwai Chung, New Territories. Lau aimed his weapon toward the radicals, who then hurled projectiles at him and tried to seize the weapon.

"I didn't fire a single shot. These young people were also somebody's children. I didn't want to hurt them," he said.

His concern for others was never repaid. Lau, who suffered a knee injury in the clash and had double vision afterward, says he's heartbroken to be condemned along with fellow officers - amid accusations of using excessive force and a widening rift that's tearing the city apart.

Radicals have turned on officers who have never been assigned to frontline crowd control operations. A 20-year-old officer, who preferred to be identified only as Ho, recalled receiving as many as 3,900 nuisance phone calls and thousands of text messages, insulting him and the entire police department, on his mobile phone over a two-week period.

Someone used his name while attempting to register for personal loans.

"Without doubt, those able to obtain that kind of information about me were people around me - ormer schoolmates or friends," said Ho.

"My mother is anxious about my safety, with protests turning into riots over the past weekends. Every morning when I leave for work, she keeps reminding me to stay safe," he said.

Since Hong Kong's radical protesters are determined to discredit and dismantle the government of the Hong Kong Special Administrative Region, undermining the morale of the police force would be a decisive step, said Tony Kwok Manwai, former deputy commissioner of Hong Kong's Independent Commission Against Corruption.

As the radicals view it, in the absence of law and order, they would be able to execute their plans at their whim, he said.

Meanwhile, Hong Kong police have arranged for retired police officers to escort the children of police officers to school, to protect them from bullying and other threats that could endanger the children.

It is part of police efforts, since the new school semester began at the beginning of September, to counter possible bullying of police officers' children.

Other measures to protect children include maintaining close contact with school management and establishing a hotline for victims of bullying. Help also is coming from the schools themselves.

"Before the new semester started, the headmaster of the school that my children go to clearly voiced support for the police force and that there are strong measures in place to protect police officers' children," said Lau, the station sergeant.

A police officer who wanted to be identified only by his surname Fong said the primary school that his 9-year-old daughter attends also has vowed to protect the children of police officers.

"But I told my daughter that her father's job is to uphold right and to stand up to tests. So I told her if her classmates ask her what kind of job her father does, she doesn't need to avoid a straightforward answer," Fong said.

Lo Wai-chung, commissioner of the Hong Kong Police Force, said earlier this week that he is confident that the police force, which has more than 30,000 members, will emerge stronger and will overcome the unprecedented challenge.