Hong Kong is bracing for its largest protest in more than a decade after nearly 800,000 voted for full democracy in an unofficial referendum, a move likely to stoke anti-China sentiment in the former British colony.
We can see that Beijing is eroding the autonomy of Hong Kong, and we want to show we don't fear central government oppression.
The annual July 1 rally, marking the day the territory returned to China in 1997, will focus on pressuring Beijing's Communist Party leaders for full electoral freedom, organisers said, and could draw the largest turnout since 2003, when half a million people demonstrated against proposed anti-subversion laws which were later scrapped.
Several groups have indicated they will stage overnight vigils after the march in a possible prelude to a planned campaign to shut down the city's financial district.
Some 792,000 people, or nearly ten percent of the city's seven million population, voted in the referendum urging Beijing to allow opposition democrats to run in a 2017 citywide election for a new leader.
The vote was organised by Occupy Central, behind the financial district shut-down plan, and comes at a time when many Hong Kong residents fear civil liberties are being stripped away.
"We can see that Beijing is eroding the autonomy of Hong Kong, and we want to show we don't fear central government oppression," said Johnson Yeung, convenor of the Civil Human Rights Front, one of the organisers of the march.
Beijing has allowed Hong Kong to go ahead with a popular vote in 2017, the most far-reaching experiment in democracy in China since the Communist takeover in 1949, but senior Chinese officials have ruled out allowing the public to nominate candidates.
Instead, Beijing says a small committee of largely pro-Beijing loyalists choose who gets on the ballot, effectively filtering out opposition candidates and consolidating the current standoff.
Hong Kong returned to China with wide-ranging autonomy under the formula of "one country, two systems", allowing such protests to take place. But China bristles at open dissent.
The stakes have grown markedly for Hong Kong and Chinese authorities over the past few weeks.
What was once dismissed as a fringe pro-democracy campaign by radicals has now snowballed into a populist movement with real clout and legitimacy.
Organisers of the Tuesday march expect more than half a million people to spill on to the streets, partly as a retort to a controversial "white paper" from China's cabinet in early June - an official government paper stressing Beijing's complete control over Hong Kong.
Two groups, Scholarism and the Hong Kong Federation of Students, say they will stage a sit-in after the July 1 march lasting until the following morning.
Alex Chow, one of the leaders of the federation, said he expected thousands to take part, with some analysts warning there was a risk this could become a catalyst for blockading the city's central business district.
In the referendum, 91 percent of voters said they wanted public nomination of candidates, while nine percent abstained.