Brutal attacks on election candidates in recent weeks have thrust the lowest tier of government in the Chinese-ruled city into the world spotlight as the government struggles to quash angry demands for universal suffrage.
Government data showed 1,524,675 people had cast their vote by 1.30 p.m., with nine hours still left until polling stations closed, surpassing the 1,467,229 people who voted in the last district elections four years ago.
First results should start trickling in before midnight.
Ming Lee, 26, said she hoped the higher turnout would benefit the pro-democracy camp that is battling some seats that were once uncontested and dominated by pro-Beijing candidates.
"I hope this vote can counter the voice of the pro-establishment, so as to bring in more voices from the democrats," she said. "The social problems encouraged people to vote and to focus on political issues."
Voter Peter Wong, 39, who works in education, said he was not optimistic for change despite the high turnout.
"I don’t mind who wins more seats as long as it’s a fair election," he said.
There was only a small police presence, in contrast to reports that riot police planned to guard all polling stations and almost the entire force of 31,000 would be on duty.
Jimmy Sham, a candidate for the Civil Human Rights Front, which organised some of the mass anti-government rallies of recent months, was beaten by men with hammers in October.
"We can see Hongkongers are longing for a chance to express their stand," he said. "We don’t know yet, at the end of the day, if the democrats can win a majority. But I hope our Hong Kong citizens can vote for the future of Hong Kong."
Beijing-backed Lam cast her ballot in front of television cameras and pledged that her government, widely seen as out of touch, would listen "more intensively" to the views of district councils.
"I hope this kind of stability and calm is not only for today's election, but to show that everyone does not want Hong Kong to fall into a chaotic situation again," Lam said.
The anti-China protests have at times forced the closure of government, businesses and schools in the city's worst political crisis in decades, as police used tear gas, rubber bullets and water cannon in response to petrol bombs, rocks and occasionally bows and arrows.
A record 1,104 candidates were vying for 452 seats and a record 4.1 million people have enrolled to vote for district councillors who control some spending and decide issues such as recycling and public health.
'FREEDOM OF SPEECH IS LOST'
If the pro-democracy campaigners gain control, they could secure six seats on Hong Kong's Legislative Council, or parliament, and 117 seats on the 1,200-member panel that selects its chief executive.
Restaurant manager Jeremy Chan saw the elections in the Asian financial hub as offering Beijing supporters a chance to share their opinions.
"They believe they are fighting for democracy, fighting for Hong Kong, but the rioters only listen to what they want to hear," said the 55-year-old, citing vandalism of businesses seen as pro-Beijing. "Freedom of speech is lost."
The protests started over a now-withdrawn extradition bill that would have allowed people to be sent to mainland China for trial but rapidly evolved into calls for full democracy, posing the biggest popular challenge to Chinese President Xi Jinping since he came to power in 2012.
Sunday was the seventh day of a stand-off at Polytechnic University, its campus surrounded by police as some protesters hid out on the sprawling grounds.
Demonstrators are angry at what they see as Chinese meddling in the freedoms promised to the former British colony when it returned to Chinese rule in 1997. They say they are also responding to perceived police brutality.
China denies interfering and says it is committed to the "one country, two systems" formula for the autonomy of Hong Kong. Police say they have shown restraint in the face of potentially deadly attacks.