Police in Hong Kong have arrested an organizer of the annual candlelight vigil remembering the deadly crackdown in Beijing’s Tiananmen Square and warned people not to attend the banned event as authorities mute China’s last pro-democracy voices.

In past years, tens of thousands of people gathered in Hong Kong to honor those who died when China’s military put down student-led pro-democracy protests on June 4th, 1989.

China’s ruling Communist Party has never allowed commemorations on the mainland, and security was increased in the Beijing square.

Efforts to suppress public memory of the Tiananmen events have lately turned to Hong Kong, where police again warned residents not to attend the vigil.

Police cordoned off parts of Victoria Park to prevent gatherings.