Tens of thousands of Hong Kong residents rallied against a proposed anti-subversion law, in the biggest public march since the mainland's takeover of the former British colony.

Organizers claimed more than 60,000 marchers – 12 times more than originally expected – turned out for the four-hour march, while police estimated the crowd at up to 12,000, according to the South China Morning Post.

The unexpectedly large turnout by a wide cross-section of society indicated that public anger was boiling over – not just at the government's failure to heed calls to protect rights and freedom, but also as a way to express grievances at government mismanagement, the paper's report said.

The march marked the latest chapter in the government's plan to implement Article 23 of the Basic Law, which aims to ban acts of treason, subversion, sedition and theft of state secrets.

The proposal has been criticised by human rights watchers and a legal expert as vague and a possible trap for the innocent. Countries including the U.S., Britain and the rest of Europe have expressed their concerns. The government plans to table a bill to the legislature in February after the three-month consultation period ends on Christmas Eve.

By early afternoon, hundreds of protesters had already assembled in Victoria Park, where more than 2,500 Christians – all wearing purple ribbons to signify hope – sang hymns and prayed against the proposal. Catholic Bishop Joseph Zen Ze-kiun, who has been vocal against the proposed law, led the prayers, reported the South China Morning Post.

"Lord, the government and its leaders were fearful of being challenged. We pray that you will dispel their fear and [that the government] will listen more with wisdom and love, so there will be better and humane protection for Hong Kong," the paper quoted him as saying.

At the other end of the park, hundreds of pro-Beijing Federation of Trade Union members staged a carnival in support of the bill.