Protesters take part in a candlelight vigil to mark the 31st anniversary of the crackdown of pro-democracy protests at Beijing's Tiananmen Square in 1989, after police rejected a mass annual vigil on public health grounds, at Victoria Park, in Hong Kong, China June 4, 2020. Thousands gathered in Hong Kong on Thursday to commemorate the 1989 Tiananmen Square Massacre, defying a ban on the event for the first time in 31 years. REUTERS/Tyrone Siu

Protesters wearing protective face masks take part in a candlelight vigil to mark the 31st anniversary of the crackdown of pro-democracy protests at Beijing's Tiananmen Square in 1989, after police rejects a mass annual vigil on public health grounds, at Victoria Park, in Hong Kong, China June 4, 2020. Police pepper-sprayed some Hong Kong protesters on Thursday who defied a ban to stage candlelight rallies in memory of China's bloody 1989 Tiananmen Square democracy crackdown, accusing Beijing of stifling their freedoms too. REUTERS/Tyrone Siu

Police officers stand guard at a candlelight vigil ahead of the 31st anniversary of the crackdown of pro-democracy protests at Beijing's Tiananmen Square in 1989, after police rejects a mass annual vigil on public health grounds, in Hong Kong, China June 3, 2020. The anniversary has struck an especially sensitive nerve in Hong Kong this year after China's move last month to impose national security legislation, and the passage of a bill outlawing disrespect of China's national anthem on Thursday. June 4 commemorations are banned in mainland China. REUTERS/Tyrone Siu

Protesters wearing protective face masks take part in a candlelight vigil to mark the 31st anniversary of the crackdown of pro-democracy protests at Beijing's Tiananmen Square in 1989, after police rejects a mass annual vigil on public health grounds, at Victoria Park, in Hong Kong, China June 4, 2020. Thousands gathered in Hong Kong on Thursday to commemorate the 1989 Tiananmen Square Massacre, defying a ban on the event for the first time in 31 years. REUTERS/Tyrone Siu

Protesters wearing protective face masks take part in a candlelight vigil to mark the 31st anniversary of the crackdown of pro-democracy protests at Beijing's Tiananmen Square in 1989, after police rejects a mass annual vigil on public health grounds, at Victoria Park, in Hong Kong, China June 4, 2020. Thousands gathered in Hong Kong on Thursday to commemorate the 1989 Tiananmen Square Massacre, defying a ban on the event for the first time in 31 years. REUTERS/Tyrone Siu

Protesters take part in a candlelight vigil to mark the 31st anniversary of the crackdown of pro-democracy protests at Beijing's Tiananmen Square in 1989, after police rejected a mass annual vigil on public health grounds, at Victoria Park, in Hong Kong, China June 4, 2020. Thousands gathered in Hong Kong on Thursday to commemorate the 1989 Tiananmen Square Massacre, defying a ban on the event for the first time in 31 years. REUTERS/Tyrone Siu