Acting police superintendent Tse Tsz-kwan said the suspect, Luk, allegedly made phone calls to cause a nuisance as he was unhappy with the rulings that the three judges gave for unrest-related cases.

Police didn't name the three judges, but district judge Stanley Chan Kwong-chi said in July that he and several other judges were harassed.

Luk, unemployed, was arrested in Kwun Tong on Monday for contempt of court and causing a nuisance. Police also seized five phones and several phone cards from him, as he allegedly used different numbers to call various government and private organizations' hotlines to request documents, and then gave the judges' office numbers to the institutions, which then faxed documents to the judges, causing a nuisance to them.

Tse said judges' phones in the office were constantly ringing, and they had to redirect the line to a fax machine to know that they received faxes from various institutions.

He added the suspect did not involve any friends and that he was not targeting judges handling the national security law.

Luk has committed offenses before, such as in 2016, when he was jailed for a month for loitering and causing concern as he followed a police inspector.

Tse reminded the public that an interim injunction has been in place since last year, which bans the public from threatening judicial officers and their family members. Those who breach the ban could be liable to contempt of court.

Under the Summary Offences Ordinance, people who make repeated phone calls to cause nuisance are liable to a fine of HK$1,000 and imprisonment of two months.

The judges' offices have been receiving many nuisance calls from October last year to July this year.

In July, Chan criticized perpetrators for breaching the law and strongly condemned their behavior, which he said affected the public's use of the judiciary services. "Heaven is always watching what you are doing," he said, adding that those who commit crimes would always be caught.

Chan said the perpetrator has committed several offenses, including harassing judicial officers, contempt of court and perverting the course of justice.

"No matter what political views you support, [such behavior] is doing comprehensive damage to Hong Kong. It's easy to destroy a system, but it takes the effort of people across several generations to build a good and effective one," Chan said.

But Chan said he did not find the nuisances to be linked to a rioting case he was handling involving three defendants.