China's Communist leaders have pulled out their usual playbook to suppress resistance to their plans to tightly limit the first direct election of Hong Kong's leader, but are likely to find that the results are quite different.

Beijing is blaming radicals and foreigners and showing off its military might, all things unlikely to go down well in the freewheeling capitalist bastion where a sizeable middle class accustomed to freedom of speech and the rule of law plans to push back with acts of civil disobedience.

Rowdy protests on Monday against a visiting Beijing official who was explaining the central government's decision signalled a new stage in Hong Kong's battle for democracy.

The ruling came after months of reminders from Beijing that it is ultimately in charge of the city despite its substantial autonomy. But the reaction in the former British colony is shaping up to be unlike anything Beijing is used to encountering when quelling dissent on the mainland.

Dozens of pro-democracy lawmakers heckled Li Fei, the deputy secretary general of the Standing Committee of the National People's Congress, or legislature, as he explained the election process, a rare occasion on which a Beijing official was exposed to open defiance.

'The central government won't budge from its stance, because it cannot allow the reins of power in Hong Kong to shift to the opposition.' - China Daily editorial

They chanted slogans and waved signs accusing China's central government of "breaking its promise" to let Hong Kong have full democracy. Security officers escorted some out and carried or dragged away others. Outside the venue, a group of activists trying to storm barricades to get inside were pepper-sprayed by police.

Democracy groups reacted with anger after Li's announcement on Sunday ruling out open nominations for candidates in Hong Kong's first direct elections in 2017. Students vowed to boycott classes, and leaders of the Occupy Central movement said the city had entered an "era of civil disobedience," adding they would go ahead with plans to paralyze the financial district with 10,000 protesters to press for genuine democracy.

Li dismissed the threats, saying "the Chinese central government believes that the Hong Kong government, especially the high-quality police force and law enforcement agencies, with the support of Hong Kong citizens, will be able to handle it."

Beijing's hard line reflects President Xi Jinping's ongoing crackdown on mainland dissent to remove all challenges to the Communist Party, as well as Hong Kong's waning importance to China as economic reforms boost other mainland financial hubs such as Shanghai.

China has sought to blame the opposition in Hong Kong on interference by Britain and other unidentified foreign forces, an echo of Beijing's frequent attacks on "overseas anti-China forces" it blames for encouraging dissidents and fuelling instability among its ethnic minorities.

It also accused Hong Kong's opposition of having become radicalized and refusing to compromise.

"No matter what the opposition does, the central government won't budge from its stance, because it cannot allow the reins of power in Hong Kong to shift to the opposition," an editorial in the China Daily said Monday.

More freedoms granted to Hong Kong activists

While some pro-democracy lawmakers are considered radical, Hong Kong democracy supporters come from a broad cross section of society, including students, religious leaders and financial workers. Occupy Central's leaders include two university professors and a clergyman.

Hong Kong activists operate openly in a way unthinkable on the mainland. Beijing exercises a broad range of punitive measures against dissidents, ranging from lengthy jail sentences to constant harassment and extrajudicial house arrest.

Political gatherings are routinely broken up, even in private homes, and protests allowed only when they align with Beijing's agenda, such as criticizing Japan or the United States. China also polices the internet for political discussions, blocks Facebook and Twitter, and demands that their Chinese equivalents report and remove any sensitive content.

Through such methods, Beijing keeps its critics fearful, impoverished and disorganized. Dissidents on the mainland are frequently charged with subversion, but also face what many consider trumped-up charges of disrupting social order, tax evasion or even organizing a crowd to block traffic.

Such restrictions are largely absent in Hong Kong. Activists are free to organize large anti-government protest rallies attracting tens of thousands of demonstrators, thanks to guarantees in the city's mini-constitution ensuring freedom of speech.

Hong Kong activists also don't face politically motivated punishment from the city's independent courts. More than 500 protesters arrested in July for staging an unauthorized sit-in following a big pro-democracy rally were charged with unlawful assembly and obstructing police, but most were later released.

A report last week that Chinese armoured personnel carriers were seen on Hong Kong's streets raised concerns that Beijing was sending a signal to the city ahead of Sunday's voting reform announcement. While the People's Liberation Army has bases in the city, it typically keeps a low profile, so the photographs of at least four of the military vehicles in the Apple Daily newspaper made democracy activists wonder about the timing.