After the rally began at around 3 p.m. local time in the Chater Garden in Central district, a large group of rioters inflicted damages on the vicinity by acts of arson and road blockage, the police said, reported Xinhua news agency.
They built barricades with railings, traffic cones and umbrellas in the vicinity of Des Voeux Road Central and Ice House Street and threw bricks onto the roads. Some threw paint bombs and defaced the exteriors of buildings in the area.
The rioters surrounded the police officers who were conducting stop and search in the area and threw water bottles and other objects at them.
Some rioters even brutally attacked two plainclothes police community liaison officers who were speaking with the organiser of the public event. The two officers, who were beaten up by rioters with wooden sticks and other weapons, sustained bloody head injuries.
"Such appalling acts are not to be condoned. The police will endeavour to bring the assailants to justice," the police said on its social media page.
The police said in its live update on the social media that it was regrettable that a peaceful public assembly was hijacked by the rioters.
In view of the violence, the police asked the organiser to suspend the public meeting and urged the participants to leave the area.
In face of the violent situation, police officers used minimum necessary force, including tear gas, to disperse and arrest the offenders.
The police warned the rioters to stop all illegal acts immediately, and warned that the participants at the scene may be liable to offenses such as unlawful assembly.
In response to the rally, the Hong Kong Special Administrative Region (HKSAR) government said in a statement released on Sunday that it deeply regrets that some participants of the public meeting had called on foreign governments to intervene in the affairs of Hong Kong and to impose sanctions.
"Foreign governments, legislatures or organisations have absolutely no role in matters relating to the constitutional development of Hong Kong and should not express any opinion or take any action in an attempt to influence or interfere in the discussions of related matters in Hong Kong," it said.
"The HKSAR government reiterates that foreign countries should not interfere in any form in the internal affairs of the HKSAR," it added.
( With inputs from IANS )