Clara Cheung looked like she'd had a bad shock.

Key points: Hong Kong pro-democracy candidates have swept the city's district council elections

Hong Kong pro-democracy candidates have swept the city's district council elections It adds momentum to the more than five-month-long protest movement

It adds momentum to the more than five-month-long protest movement An observer says more protests may result unless Chief Executive Carrie Lam makes changes in response to the results

Counting in the Hong Kong suburb of Happy Valley had just revealed that she was the winner in the district council election, ousting a pro-establishment dynasty who'd held a tight grip on the seat for three decades.

Her supporters whooped with joy.

"Clara, Clara, Clara!", they chanted, as she shook hands with the losing candidates.

Clara, a 40-year-old mother of two, part-time lecturer and art curator, looked drained and seemed momentarily on the verge of tears.

She had hoped to win, of course, but "I didn't try to expect anything".

Pro-democracy candidates took a significant early lead after residents turned out in record numbers. ( ABC News: Brant Cumming )

It was a victory both locally and for Hong Kong, she said.

"The neighbours also told me besides voting for the local issues, they are also voting for the Hong Kong situation."

"It's actually about the solidarity for the Hong Kong people," she told the ABC, and then was lost for words.

"That's it for now, because I'm maybe a bit overloaded," she said, backing away.

As Happy Valley was being declared, results elsewhere were just starting to trickle in from the labyrinth of polling stations across the city.

Pro-democracy candidates took 385 seats, or about 85 per cent of the spots up for grabs. ( ABC News: Brant Cumming )

The picture emerging was taking everyone by surprise.

A pro-democracy landslide

In the end, it was a drubbing on a monumental scale.

Pro-establishment candidates saw their bloc of seats slashed from the hundreds to the dozens.

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Even seasoned observers were taken aback.

"I think it's kind of surreal," said Ma Ngok, a respected political scientist from the Chinese University of Hong Kong.

Associate Professor Ma said he stayed up until about 4am and then decided to call it a night when the scale of the swing was no longer in doubt.

This was not an early lead, but a landslide.

"It is an unprecedented victory for the democrats in the electoral history of Hong Kong," he told the ABC.

He said he expected the newly-minted pan-democracy councillors to come up with a list of demands on democracy and freedoms for Carrie Lam's Government.

Ma Ngok said the result was an "unprecedented" pro-democracy victory. ( ABC News: Brant Cumming )

If there was no movement in these areas, it may not be long before the uneasy peace of the past days in Hong Kong was broken, he said.

"If the electoral councillors put forward demands and then the government doesn't make any significant gestures to respond to them, then we may expect some other actions by the end of the week."

Young protesters celebrate and renew momentum

Across town, a teenage boy had also not slept much, not at all in fact, he told me on a messaging app.

"John," as we've agreed to call him, said watching the results come in "was an unforgettable experience".

A week ago the 17-year-old was holed up inside the Polytechnic University, one of hundreds of protestors who laid siege to it.

At least 2.94 million people voted, a record turnout of more than 71 per cent. ( Reuters: Athit Perawongmetha )

He said he managed to escape the university last Monday.

The gains for pro-democracy candidates have only added momentum to the cause, he said.

"This shows that the general public stands with the protestors firmly and it adds much confidence to me and my fellow friends," he wrote, before signing off to go and prepare for a Chinese language exam at school.

It's been a day of celebration for those who have taken part in and supported the more than five-month-long protest movement.

Champagne and bonhomie have been in ample supply.

The vote in itself has changed nothing yet though, and the "five demands, not one less" mantra of the movement remains.

In the short term, all eyes will be on Chief Executive Carrie Lam's weekly presser on Tuesday morning (local time).

In a statement released on Monday, Ms Lam said the government would "respect" and "reflect on" citizens' views.

Her detractors say the time for reflection is long past.

'She should have stepped down long ago," Professor Ma said.

"I don't see that she can actually govern… but it is Beijing's call."