Veteran Hong Kong activist Koo Sze-yiu was denied bail on Saturday after being taken to court by national security police to face a charge of attempting to commit a seditious act.

The legal document available at Kowloon City Court did not spell out the specific act Koo, 75, was accused of, except that it occurred “on or about the 4th day of February in Hong Kong”.

Koo was arrested on Friday shortly before he planned to stage a protest against the Winter Olympics which opened in Beijing on the same day.

He was charged with one count of “attempting to do or making any preparation to do an act or acts with seditious intention” under the Crimes Ordinance, an offence punishable by up to two years in jail.

Prosecutors argued that by committing the alleged seditious act, Koo had brought, among other things, hatred and contempt against “central authorities” and the Hong Kong government and judiciary.

It could also raise discontent among Hong Kong residents or “counsel disobedience to the law”.

Acting chief magistrate Peter Law Tak-chuen, among those hand-picked by the chief executive to hear national security cases, rejected his bail application, saying that the allegation was “very serious”.

Prosecutors said they needed time for further investigation and forensic examinations of items seized from Koo’s home, including a coffin with the words “human rights is above the Winter Olympics”.

Law adjourned the case to April 1.

In a statement on Saturday, police said their National Security Department had charged a 75-year-old man under the Crimes Ordinance.