The son of kung fu star Jackie Chan was sentenced to six months in prison on Friday after admitting drugs offences, a Beijing court said.

Jaycee Chan, who like his father has worked as an actor and singer, will be released in mid-February, having already spent five months in jail.

State broadcaster China Central Television showed Chan pleading guilty in court, wearing a black jumper and blue trousers, flanked by two policemen.

"I broke the law," he said, appearing attentive and respectful of the proceedings. "I deserve to be punished. When I return to society, I definitely won't do it again."

Chan was detained in August and charged with providing a venue for others to use drugs after police said they found 100 grams (3.5 ounces) of marijuana at his home in the Chinese capital.

An hour and 22 minutes after proceedings began, the Dongcheng District People's Court posted on a verified social media account: "He was convicted. He has been sentenced to six months in jail and fined 2,000 RMB," or renminbi ($320).

The court also said that his "detention" will end on February 13.

Chan and Ko Chen-tung, a Taiwanese actor also known as Kai Ko, both tested positive for marijuana according to state media, and Kai made tearful televised confessions.

At least 10 locally known stars were detained on drug-related charges last year, state-run media have said.

The arrests have been seen by observers as part of a wider campaign on morals by Beijing, which has also targeted prostitution and the wider drugs trade.

Around 200 mainly domestic journalists at the Dongcheng court were allowed to set up their equipment outside the building as the defendant arrived, and reporters were invited to wait in a conference room in the court building, where staff gave updates while handing out bottled water and tea.

The scene was far removed from trials of Chinese dissidents, which domestic journalists generally do not attend except for a select few from state-run outlets.

Foreign journalists at sensitive hearings are often aggressively targeted by plain clothes police if they go within even a few blocks of the courthouse.

Jaycee Chan has featured in several films but has not so far won the acclaim earned by his father, one of Asia's best-known actors with a string of Hollywood hits to his name.

Shortly after his son's detention, Jackie Chan said in a post on China's Twitter-like Sina Weibo that he was "extremely angry and extremely shocked".

"As a public figure, I am ashamed. As a father I feel terrible," he said in August.

A total of 7,800 people were arrested for drugs offences in Beijing between January and August last year, state media reported, an increase of almost 72 percent on the same period in 2013.

There were 26,000 "registered cases" of drug use in Beijing in 2014, up 10 percent year-on-year, according to police, who claim "singers, actors and film directors" comprise 0.15 percent of drug users in the city.

Use of recreational drugs has risen in recent years in China as an economic boom has boosted the middle classes' disposable income.