Six people have been arrested in Hong Kong as authorities moved to restrict public commemoration of the Tiananmen Square massacre.
Saturday was the 33rd anniversary of the highly sensitive incident in which China's rulers crushed peaceful protests with tanks and troops.
Until recently, Hong Kong was one of the few Chinese territories which commemorated the event.
But Beijing has effectively banned the city's annual public vigil.
Hong Kong Police confirmed five men and one woman had been arrested in the vicinity of Victoria Park, where a candlelight vigil marking the 1989 crackdown in Beijing would have been held.
The six are now in police custody.
Some images shared on social media appeared to show people being detained and led away by police officers in the city. Others were seen being searched.
Hundreds of police, some with sniffer dogs, were also seen patrolling the area around the park in the evening.
Dozens of people - in an apparent attempt to replicate the annual candlelit vigil - turned on their mobile phone torches in an area near to the park on Saturday. They were then warned by police to turn them off, Reuters news agency reports.
Officials earlier warned that any unauthorised assembly could see demonstrators facing prison sentences of up to five years.
"For 33 years it has always been peaceful, but today it's like [the police] are facing a big enemy," one activist, Chan Po-ying, told AFP. "The hearts of people will live on."
The Tiananmen Square protests in Beijing became the focus for national demonstrations calling for greater political freedoms in 1989. Thousands of people - mainly students - camped for weeks in the square before the military moved in on 4 June and opened fire.
One unidentified protester became an international symbol of protest for blocking an advancing column of tanks in video footage which was seen around the world.
The Chinese government says 200 civilians and several dozen security personnel died. Other estimates have ranged from hundreds to as many as 10,000.
The actions of the authorities have been seen by activists as part of China's broader agenda to snuff out political dissent in Hong Kong.