Striking students marched on Hong Kong's financial district Wednesday, taking their protest for greater democratic rights to the commercial centre for the first time.

Student groups are currently spearheading a civil disobedience campaign by a coalition of democracy activists protesting against a recent decision by Beijing to vet who can stand for the city's top post at the next election.

University students began a week-long class boycott on Monday, rallying a crowd that organisers said was 13,000-strong on a campus in the north of the city and breathing new life into a movement that had been stunned by Beijing's hardline stance.

On Tuesday the students moved their protest to a public park outside the main legislative complex of the semi-autonomous Chinese city, briefly mobbing current Hong Kong leader Leung Chun-ying as he exited the building.

Around 500 students and supporters Wednesday made their way from Tamar Park to Central business district, where many big international companies are based.

Shouts of "We want democracy!" amplified by bullhorns echoed around the district famously dominated by towering skyscrapers.

"This march is to show the rich, the people working in Central, the people with real power in Hong Kong, that they can't ignore this grassroots movement," said Nathaniel Siu, 18, an applied social science student at Hong Kong Polytechnic University.

Siu said his mother, who works in one of the office buildings along the protest route, does not approve of his activism and dinner conversations have become increasingly awkward at home.

"Walking to Central shows more people we really care about democracy, that we're serious. We're not just sitting in a park anymore," said Tiffany Fong as she pointed a handheld fan at her face in the humid weather.

The students ended their march without incident, gathering back in Tamar Park where regular lectures are being held.

- Group hints at takeover date -

Occupy Central, a prominent grassroots pro-democracy group, has vowed to take over Central if its demand that Hong Kongers be allowed to nominate candidates for leader is not met.

Last month China said Hong Kongers would be allowed to vote for their leader for the first time in the 2017 election, but that only two or three candidates approved by a pro-Beijing committee could stand.

The students are not expected to engage in direct action imminently. Federation of Students leader Alex Chow has given Leung until Thursday morning to meet their delegates. If he refuses, Chow said, students will intensify their actions.

Students outside the legislative building chanted taunts against Leung Wednesday, calling him a turtle unwilling to come out of his shell and meet them.

"I don't think this protest will gain us more freedoms, but we can't just lay down and do nothing while the Chinese government tramples over us," said Karena Sun, a third-year nursing student.

Occupy co-founder Benny Tai has hinted that the takeover of Central could begin on October 1, a national day holiday when much of the district will be empty.

"While others are celebrating the big day of the country, we will set up a grand banquet in Central to fight for Hong Kong's democracy," he wrote in the Apple Daily tabloid earlier this week.

The students plan to keep their protest in the park opposite the legislative building going until at least Friday, with a series of public lectures and speeches.

Britain handed Hong Kong back to China in 1997 under a 'one country, two systems' agreement which allows it civil liberties not seen on the mainland, including free speech and the right to protest.

But tensions have been growing over rising inequality and Beijing's perceived political interference.

During one point on Wednesday's student march an AFP reporter heard a tourist from mainland China tell his son in Mandarin: "They don't want Hong Kong to become like China."