Protesters yesterday accused police of taking a heavy-handed approach during demonstrations against Beijing's stringent restrictions on Hong Kong's democratic reform.
A series of protests have taken place since Sunday, when the National People's Congress Standing Committee set its rules for the 2017 chief executive poll, many of them targeted at Li Fei , a senior Beijing official sent to Hong Kong to explain the ruling.
There were two nights of stand-offs outside the Wan Chai hotel where Li was staying, and pepper spray was deployed as he spoke at a forum at AsiaWorld-Expo on Monday.
Among those arrested was performance artist Au Yeung Tung, who protested against what he called Beijing's "naked tyranny" by stripping off outside government headquarters in Admiralty as Li gave a press conference inside on Monday.
Au Yeung said officers put him in a police vehicle and then spent about 20 minutes discussing what charge they could arrest him for.
They considered indecent exposure and disorderly conduct, but settled on outraging public decency, a more serious offence that can carry a jail term of up to seven years.
"I think this is a warning [to protesters] from the police … why did they use the most serious offence to arrest me?" Au Yeung said outside Central Police Station, where he was released in the early hours of yesterday.
Watch: Scholarism protest against NPC decision outside of Beijing official Li Fei's hotel on Sunday night
A police spokeswoman said Au Yeung had refused to accept bail, but officers decided to release him without bail conditions. The investigation was continuing and the force reserved the right to charge him, she added.
Four men, aged 18 to 21, were also arrested at Asia World-Expo on Monday and yesterday, and three were released on bail.
Separately, 19 people were arrested late on Monday night outside the Grand Hyatt, where Li was staying. At one point, protesters charged police lines at the hotel, which was also the site of student protests on Sunday.
Wong Yeung-tat, of Civic Passion, was arrested for obstructing police. The rest were detained for taking part in an unlawful assembly.
Wong said the arrests were unreasonable. "Our members were leaving the area after the protest but police surrounded them and did not let them go," Wong said. "I was arrested minutes after I arrived for asking what was going on."
The 15 men and four women, aged 20 to 45, were released on bail.