Hong Kong, China (BBN)-Hundreds of thousands cast ballots in Hong Kong in an unofficial referendum on how its leaders should be chosen, reports Juliana Liu, as turnout far exceeds expectations.

Despite what organisers called the biggest cyber attack in Hong Kong's history, hundreds of thousands of people have been able to voice their opinion in an unofficial pro-democracy referendum that started on Friday, reports BBC.

As of 21:00 local time (14:00GMT) on Sunday, 689,000 ballots had been cast in the city-wide vote organised by the Occupy Central movement.

The high turnout has far exceeded expectations. Organisers said they would have been happy with at least 100,000 votes.

The actual voting, both online and in person at 15 polling stations scattered across Hong Kong, was overseen by Robert Chung, an experienced pollster from the University of Hong Kong.

He told me the system had originally been designed to handle a maximum of 800,000 votes.

No one had expected so many ballots to be cast just three days into the 10-day voting exercise.

"It is approaching the technical limit of our design so I would say the turnout so far is surprisingly high," he said at a polling station in the Causeway Bay neighbourhood.

'REAL DEMOCRACY'

One of the voters was 25-year-old financial analyst Natalie Cheng, who came to vote with her friends.

Unable to successfully cast a ballot online because of heavy traffic and a continuing cyber attack, she decided to visit a polling centre.

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"We want freedom. We want real democracy. That's why we're here," she explained.

"In three years, the list of candidates the Chinese government will give us will probably be approved by the Chinese government, not approved by us. And it's not fair. We won't be able to vote for a real (chief) executive. This is not real democracy."

She chose the first of the three proposals on the ballot. All of them involve allowing the public to nominate the candidates for chief executive in 2017.

That Natalie and her friends were allowed to publicly vote in a large-scale poll organised by political activists is, in itself, an example of Hong Kong's unique status in China.

As a condition of the former British colony's return to China in 1997, it was promised special rights and privileges, including full universal suffrage.

The Chinese government has agreed that in three years, the next chief executive would be elected directly by the city's 3.5 million voters.

But officials insist the candidates must be shortlisted by a nomination committee, as spelled out in the Basic Law, the constitution that governs Hong Kong.

Pro-democracy activists fear the way the Chinese government interprets the law will result in what they consider a sham election, with voters allowed to choose from only a list of loyalists whose sympathies lie with Beijing.

Benny Tai, a law professor who started the Occupy Central movement, said his goal was to put pressure on the Chinese government to implement an 'internationally accepted' form of universal suffrage.

The official Xinhua news agency has called the referendum "illegal" and "invalid".

But Tai said even if the referendum were not legally binding, the strong turnout could not be ignored.

"They have clearly indicated their view that they deeply want true democracy for Hong Kong," he said. "Any responsible government cannot ignore or undervalue their views."

The Hong Kong government ended a five-month public consultation on the future of political reforms in May.

Later this year, it is expected to unveil its own electoral reform proposal, which must be approved by two-thirds of lawmakers.

Tai has indicated that if the proposal does not satisfy international standards, then Occupy Central may mobilise thousands of supporters to paralyse the Central business district in a civil disobedience campaign.

Over the past 35 years, the Chinese Communist Party has been experimenting with economic reforms in designated areas, before popularising them elsewhere.

But the unexpectedly large turnout by the Hong Kong public suggests the party may be much less surefooted in experimenting with political reforms, especially in a city with established freedoms of speech and assembly.

BBN/ANS-23June14-4:40pm (BST)