Thousands of students converged on a university campus in Hong Kong today, launching a week-long boycott of classes in protest against Beijing's decision to rule out fully democratic elections in the former British colony.

Students from more than 20 universities and colleges streamed into the grounds of picturesque, bay-side Chinese University of Hong Kong, where they were greeted by banners that said: 'The boycott must happen. Disobey and grasp your destiny.'

Some sat in a circle playing guitars, while others folded leaflets urging students to boycott classes in a protest which coincides with a trip to Beijing by some of Hong Kong's most powerful business tycoons, who are expected to talk about government policies with Chinese leader Xi Jinping.

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Thousands of Hong Kong students gather at the Chinese University of Hong Kong to protest Beijing's decision to rule out fully democratic elections in the former British colony

Students folded leaflets, played guitars and sang freedoms songs during the mass protest

Hong Kong returned to Chinese rule in 1997 with a high degree of autonomy, but Beijing's rejection of the right to freely choose the city's next leader has prompted threats from activists to occupy and shut down the Central finance district as part of their pro-democracy campaign.

Beijing decided in August to rule out open nominations for candidates under proposed guidelines for the first-ever elections to choose the city's top leader, which have been promised for 2017.

The National People's Congress, China's legislature, instead insists that candidates be vetted by an elite committee that is similar to the body of mostly pro-Beijing elites that has until now selected the city's leaders.

Democracy groups reject such screening for loyalty to Beijing and demand elections that offer a genuine choice.

The strike marks the beginning of a week-long boycott of university classes being backed by academics

The action coincides with a visit to Beijing by some of Hong Kong's wealthiest business tycoons to discuss government policy with Chinese leader Xi Jinping

'I believe on August 31, when the National People's Congress made their decision, it crushed the dreams of some Hong Kong people who have been fighting hard for democracy for the past 30 years,' said third-year student Hong Yuen.

Leading academics in Hong Kong have voiced support for the boycott, with some offering to record lectures and post them online for students who miss school to watch later.

About 380 academics and other school staff have signed a petition supporting the students, saying they should not 'stand alone'.

'At the minimum, [the strike] can provide a wakeup call to tens of thousands of university and secondary school students in Hong Kong,' said Dixon Sing, a professor at Hong Kong University of Science and Technology and one of the organisers of the signature campaign.

He added that the organisers are 'trying to inspire many other fellow classmates to be aware of and be devoted to the democratic movement'.

One in five people say they are considering leaving Hong Kong because of concerns over its political future

The boycott is being organised by groups such as the Hong Kong Federation of Students and Scholarism.

A survey by the Chinese University showed more than a fifth of Hong Kong residents are considering leaving the city, spurred by concerns over its political future.

Residents overall feel pessimistic about the current political climate, according to the poll, released yesterday. On a scale of zero to 10, with zero being 'extremely pessimistic', the average response was 4.22.

However, about 46 per cent said they did not support the movement to occupy the Central finance district.

'Hong Kong is on the brink of another wave of mass migration,' said Sonny Lo, a professor at the Hong Kong Institute of Education who is unaffiliated with the poll.

'More and more people will leave in the next few years as the election for the chief executive approaches.'

The city saw waves of migration leading up to the transfer of sovereignty from the UK to China in 1997, when tens of thousands left every year.

Emigration also surged in the wake of the Tiananmen crackdown in 1989, when Beijing violently suppressed protests by thousands of students calling for democracy.

Many went to Canada, Australia and the US, only to return later as the political and economic situation in Hong Kong stabilised.