One of the attendees, a 27-year-old man surnamed Wong, said there was no reason to defile the national flag, a symbol of the country. He asked the city's young people to calm down and think about their futures as well as the city's.

In a statement issued early Sunday, the SAR government spokesperson strongly condemned the profaning of national flag, saying the vandals have blatantly breached public peace and challenged national sovereignty. The government pledged to strictly enforce the law, the spokesperson added.

Lawrence Ma Yan-kwok, president of the Hong Kong Legal Exchange Foundation, said the suspects have breached the National Flag and National Emblem Ordinance and could face a sentence of up to three years.

In a statement, the Hong Kong Federation of Trade Unions condemned those behind the scenes for using young people to challenge national sovereignty and the principle of "one country, two systems".

The largest labor union in the city urged the government to take serious action to safeguard the city's stability and peace, as well as the nation's sanctity.

Outraged by what the New People's Party described as "lawless" behavior, the party said the act constituted blatant defiance of national sovereignty and the perpetrators should be brought to justice as soon as possible.

Tang Fei, former president of the Hong Kong Federation of Education Workers, said it is unacceptable for radical protesters to repeatedly defile the national flag and national emblem.

Since the middle of June, violence and vandalism by radical protesters against the government's now-suspended extradition bill escalated. They, in a well-equipped and organized manner, mounted sustained assaults on the police and government. Some were arrested for possession of explosives in what is believed to be one of the protesters' warehouses.

Two similar protests — one in Tseung Kwan O and the other in Western Hong Kong Island — were planned for Sunday afternoon. A massive strike was also planned for Monday, despite strong criticisms from the community over sustained traffic disruption during the past two months.