Beijing official heckled amid Hong Kong election anger
Pro-democracy activists in Hong Kong have disrupted a speech given by a Beijing official explaining voting changes for the territory.
They chanted slogans and held placards accusing Beijing of breaking its promise to allow Hong Kong to choose its leader directly.
On Sunday the Chinese government ruled out open nomination of candidates for the chief executive election in 2017.
The move sparked anger among pro-democracy groups.
The disruption took place as Li Fei, deputy secretary general of China's National People's Congress Standing Committee, prepared to address Hong Kong officials.
Agencies reported that as Mr Li approached the lectern, several lawmakers and demonstrators stood up with placards and a banner, chanting: "The central government broke its promise, shameless." They were eventually escorted out by security guards.
Mr Li continued with his speech, saying any leader who wished "Hong Kong will become an independent political entity or will change the country's socialist system will not have a political future".
A large group of pro-democracy activists were amassed outside of the hall. Police used pepper spray on at least four activists when a group attempted to force their way into the hall, according to the South China Morning Post.
A small number of pro-Beijing activists also briefly clashed with the opposing camp. The presence of activists from both sides was a reminder of how politically polarised Hong Kong has become, said the BBC's Juliana Liu.
The issue of how Hong Kong should choose its next leader has gripped the territory in recent months, triggering several protests and large-scale rallies from both pro-democracy and pro-Beijing camps in recent weeks.
China had promised that the people in Hong Kong, whose chief executive has in the past been chosen by a small group of the elite, would be able to elect their leader by 2017.
But on Sunday it said candidates would need the support of more than 50% of a nominating committee to run in the election, and that only two or three would be selected.
Critics expect the committee to be heavily tilted in favour of Beijing loyalists, giving Beijing an effective veto over candidates.
Carrie Gracie, BBC China editor
Beijing's uncompromising stance on Hong Kong is part of a wider political picture.
Under the leadership of Xi Jinping, China itself has moved further against any suggestion of democratic reform, the Communist Party ever more jealously entrenching its own monopoly on power.
Hong Kong is the only place where Chinese citizens can criticise the one party-state or commemorate the Tiananmen democracy protests of 1989.
Free speech and freedom of assembly in the former British colony already stretch Beijing's patience, and - although it does not wish to renege from the promise of direct elections for the next chief executive of Hong Kong in 2017 - it is not prepared to risk the emergence of a leader who might confront its own interests outright.
In the last election, candidates required only 12.5% of votes from an election committee to qualify. That committee would then go on to pick the chief executive from the pool of candidates.
Mr Li said the new rules would reduce the risk of populist candidates being selected, and were in line with Hong Kong's mini-constitution, the Basic Law, which states that candidates must be selected by "democratic procedures".
Angry activists have vowed to set in motion an "era of civil disobedience" with a series of actions aimed at occupying the main financial area of Hong Kong.
Organisers of the main protest group, Occupy Central, have not disclosed when they will stage the sit-in but said they will give more details in coming weeks.
China state media outlets, meanwhile, hailed the announcement, with Xinhua news agency saying that allowing Hong Kong to elect its leader was a "solemn promise from the central government to all the people in Hong Kong".
In Hong Kong, Ming Pao daily expressed disappointment and foresaw instability.
It said it hoped activists would stick to "non-violent methods to fight for democracy and draw a line from the radical forces to prevent Hong Kong from descending into chaos".