Given a chance to vote, the people of Hong Kong did just that.

Long lines snaked around plazas and extended for blocks as citizens of the semi-autonomous Chinese territory turned out in droves on Sunday for an election seen as a test of public support for anti-government protests that have persisted for more than five months.

The Electoral Affairs Commission said 31 per cent of the city's 4.1 million registered voters cast ballots in the first five hours, up from 14.5% in the same period four years ago.

Christina Li said that it was important for older people like herself to support the youth, who are at the forefront of the protests.

'Younger generations might not be able to enjoy the rights that we are enjoying now,' she said as she waited in line to go inside a polling station. 'We cannot take it for granted.'

The race for 452 seats in the city's 18 district councils has taken on symbolic importance. A strong showing by the Opposition would show that the public still supports the pro-democracy movement, even as the protests have become increasingly violent.

The vote for the district councils, which advise the government on issues of local concern, are the only fully democratic elections in Hong Kong. Members of the legislature are chosen partly by popular vote and partly by interest groups representing different sectors of society, and the city's leader is picked by a 1,200-member body that is dominated by supporters of the central government in Beijing.

The ruling camp in Hong Kong and the government in Beijing hope that the unrest and disruption to daily life will turn voters against the protesters.

Democracy activist Joshua Wong, who was barred from running in the election, voted soon after polls opened at 7:30 am. Results are expected after midnight.

'Even if they censor me out from the ballot, lock me out in prison, it will just encourage me to continue to fight for the future with even stronger determination,' he told reporters.

City leader Carrie Lam said after voting that organising the election was extremely challenging because of the unrest.

'But I'm pleased to say that ... we should have a relatively peaceful and calm environment to conduct these elections successfully,' she said.

The district councils advocate for community interests and are given a small budget for local projects. Successful candidates will serve a four-year term beginning January 1.

There has been a rare break in the violence in recent days as protesters, anxious to validate their cause through the ballot box, hit the pause button to ensure the polls won't be postponed.

Government officials had earlier warned that the election could be called off if the violence did not subside.

'We need to show the world that our cause is legitimate. I don't believe that Beijing will not respond to the Hong Kong people's voice,' a black-clad and masked student Alex Wong said during a peaceful march Saturday.

Hong Kong chief secretary Matthew Cheung said that a strong police presence at polling stations will ensure that the vote proceeds smoothly.

Online messages from protest support groups have advised people not to wear black or face masks during voting in case they are targeted by police.