Hong Kong independence activist Andy Chan attacked China as an empire trying to "annex" and "destroy" the city in a no-holds barred speech Tuesday at the city's press club which Beijing wanted cancelled.
In comments that will incense Chinese authorities, Chan, who leads the tiny Hong Kong National Party, said Beijing was semi-autonomous Hong Kong's "colonial master".
"We are a nation that is quickly being annexed and destroyed by China," Chan told a packed Foreign Correspondents' Club.
He said he had been under increased "surveillance" by groups of people he did not know, who had been following him and knocking on his family's door to take pictures of them in the lead-up to the speech.
Hong Kong enjoys freedom of speech and assembly unseen on the mainland under a handover agreement between Britain and China.
But Beijing has become increasingly intolerant of any mention of independence for Hong Kong as President Xi Jinping emphasises territorial integrity as key to China's resurgence.
Rival protesters gathered outside the FCC, with pro-independence activists clashing with police, saying they had been given no space for their rally, while dozens of pro-Beijing supporters chanted slogans including "Gas the spies!"
The lunch address -- entitled "Hong Kong Nationalism: A Politically Incorrect Guide to Hong Kong under Chinese Rule" -- drew objections from China's foreign ministry and Hong Kong's leader Carrie Lam, as fears grow that freedom of speech in the semi-autonomous city is increasingly under attack.
The club stood by its decision to go ahead with the event, saying the views of different sides in any debate must be heard.
Chan called on Britain and the United States to help Hong Kong and said Taiwan was an inspiration for his party as it had gone from a dictatorship to a democracy.
China still sees self-ruling Taiwan as part of its territory awaiting reunification, using force if necessary.
Ahead of Chan's talk China's foreign ministry had said: "We resolutely oppose any external forces providing a platform for 'Hong Kong independence' elements to spread fallacies."
- Party ban -
The Hong Kong government said Tuesday that while it backs freedom of the speech and the press, it "deeply regrets" the event since advocating independence contravened the city's Basic Law, or mini-constitution.
"It is totally inappropriate and unacceptable for any person to openly promote and advocate the independence of Hong Kong," a spokesman said.
"As such, it is also totally inappropriate and unacceptable for any organisation to provide a public platform to espouse such views."
Chants from protesters outside could be heard throughout Chan's address.
A small group called the Students Independence Union turned out in support of Chan, waving independence banners outside the club in Hong Kong's Central district.
Other pro-democracy protesters said they did not support independence but were supporting Hong Kong's right to freedom of the press and freedom of speech.
The pro-Beijing groups gathered outside waved China's national flag, chanting "Get out of Hong Kong! We Chinese people don't welcome you!", describing the FCC as "thieves" and demanding the government "take back" the colonial-era FCC building it leases to the club.
Chan's Hong Kong National Party is facing a ban from city authorities who say it is a threat to public security despite having only a dozen core members.
It is the first time such a ban has been sought since Britain handed over Hong Kong in 1997.
Asked about whether Chan agrees with calls from some in the independence movement for radical action, Chan said he "condemned violence".
Calls for the city's independence have infuriated Beijing even though they attract little support.
Chan was banned from standing for office in 2016.
His talk was part of the FCC's "club lunch" tradition which has seen an array of speakers, including Chinese officials, speak to members and the media.