Chinese President Xi Jinping has warned that any efforts in Hong Kong "to challenge the power of the central government" are "absolutely impermissible", as the territory on Saturday marked 20 years since its handover to Beijing from Britain.
Their target was an object associated with state power: the Golden Bauhinia statue, a floral sculpture more than 15 feet high that Beijing gave to Hong Kong, a symbol of the city's 1997 transformation from a British crown colony into a special administrative region of the People's Republic of China.
"In the past two decades, Hong Kong has developed from a regional market with regional companies listed on the exchange for local investors and limited foreign investor involvement into an worldwide financial center".
But the march, which saw banners with the slogans "Democracy Delay No More!"
"What we've experienced this weekend was a whole new level of intimidation and direct violence that's unprecedented", said campaigner Avery Ng of League of Social Democrats.
At midnight on June 30, 1997, after sampling a curry dish and a rum punch at the Regent Hotel, the main Chinese and British authorities attended the act that would forever change the course of Hong Kong.
One protester carried a cardboard cutout of Xi holding a yellow umbrella - symbol of the 2014 pro-democracy Umbrella Movement which brought parts of the city to a standstill.
Scores of democracy protesters were taken away by police, while several pro-China groups remained, cheering loudly and waving flags as though in victory.
On the same day, hundreds of people from the Chinese communities of the San Francisco Bay Area gathered at the Chinese consulate in San Francisco to celebrate the 20th anniversary of the return of Hong Kong to the motherland. "The message is clear: when all else fails, the army is the last resort", said Willy Lam, a Hong Kong political analyst, to Ap.
"Self-determination" and pro-Beijing groups taunted each other, with hundreds of police deployed on a traditional day of protest in Hong Kong.
He believed the new chief executive, Carrie Lam Cheng Yuet-ngor, was now entrusted with two missions - enactment of Article 23 of Hong Kong's Basic Law - which requires the city to enact its own national security law to ban treason, secession, sedition or subversion - and the launch of national education in the school curriculum.
But as Beijing's influence grows, many feel it is just a matter of time before the city merges into mainland China.
Mr Xi said Hong Kong should crack down on moves towards "Hong Kong independence".
That, combined with Xi's visit, had sharpened the mood for this year's march, said one veteran participant, retiree David Tse.
In response to the U.S. and United Kingdom statements, Chinese foreign ministry spokesman Lu Kang detailed Hong Kong's "comprehensive achievements with the support of the central government and mainland".
They demanded the release of cancer-stricken Chinese dissident Liu Xiaobo, who remains on medical parole on the mainland, and that China take responsibility for the brutal Tiananmen crackdown against student democracy protesters in Beijing in 1989.
He was briefed on how the Hong Kong Special Administrative Region Government, through investment in infrastructure, is enhancing its connections within the Guangdong-Hong Kong-Macao Bay Area as well as with the rest of Mainland, and on the strategy of strengthening Hong Kong as an worldwide and regional logistics hub. Now, here on the trading floor in Hong Kong, he says, they're more like servants.