The city last held district council elections at the peak of huge, sometimes violent, democracy protests in 2019, recording a historic-high 71 percent turnout that delivered a landslide victory for the democracy camp.

But a clampdown on dissent -- aided by a sweeping national security law imposed by Beijing in 2020 -- has included a drive by authorities to weed out from public office anyone deemed politically disloyal after the protests.

Police acted swiftly to clamp down on any sign of dissent on Sunday, arresting at least six people in an exercise that officials said drew just shy of 1.2 million out of 4.3 million registered electors to the polls for a final turnout of 27.54 percent.

Previously, the lowest turnout since the city's handover to China was 35.82 percent, recorded in 1999.

Beijing's top office overseeing Hong Kong on Monday congratulated the city for holding an election that "uplifted the spirit and consolidated consensus", adding that the vote "injected strong momentum" for the city's development.

City leader John Lee had earlier said that this year's election was "the last piece of the puzzle to implement the principle of patriots administering Hong Kong".

"From now on, the district councils would no longer be what they were in the past -- which was a platform to destruct and reject the government's administration, to promote Hong Kong independence and to endanger national security," Lee said after he cast his ballot on Sunday.

- 'Hugely humiliating' -

John Burns, an emeritus professor at the University of Hong Kong, said the record-low turnout may "reveal citizens' widespread scepticism" about whether the district councils could reflect their views.

"The public turned its back on the polls, effectively saying 'the polls have little to do with us,'" Burns told AFP, adding that the result showed the local government's "weak mobilisational capacity".

Kenneth Chan, a political scientist at the Baptist University of Hong Kong, said the turnout was "hugely humiliating" to the authorities.

According to new rules announced in May, the number of seats that could be directly elected was slashed from 462 to 88, with the other 382 seats controlled by the city leader, government loyalists and rural landlords.

Candidates were also required to seek nominations from three government-appointed committees, which effectively shut out all pro-democracy parties.

Over 70 percent of the candidates picked to run for the election were themselves members of the nominating committees.

Police deployed in force on Sunday and arrested at least six people, including three members of the League of Social Democrats, one of the city's last remaining opposition groups.

Their case was taken up by Hong Kong's anti-graft agency, which said the trio was suspected of "inciting others not to vote".

On Monday, veteran activist Koo Sze-yiu, 77, was denied bail after he was charged with "attempting or preparing to do an act with seditious intention".

The three League of Social Democrats activists and Koo had told media they planned to stage protests but were all arrested before they could show up.