By James Pomfret and Greg Torode
HONG KONG (Reuters) - Hong Kong holds a controversial "referendum" on democracy on Friday, a prelude to an escalating campaign of dissent that could shut down the former British colony's financial district and further anger China's Communist Party leaders.
An affluent city of seven million that returned to Chinese rule in 1997, Hong Kong's longstanding push for full democracy is reaching what could be boiling point with tens of thousands expected to vote in the unofficial referendum.
While Beijing has allowed Hong Kong to go ahead with a popular vote for the city's top leader in 2017, the most far-reaching experiment in democracy in China since the Communist takeover in 1949, senior Chinese officials have ruled out allowing the public to nominate candidates.
Instead, Beijing insists a small committee of largely pro-Beijing loyalists choose who gets on the ballot, which would effectively render the ability to vote meaningless.
One of the founders of the so-called Occupy Central protest movement, academic Benny Tai, hopes its referendum will draw up to 300,000 people to strengthen the legitimacy of the group's demands for a fair and representative election in 2017 that would include opposition democrats.
The online vote, which is due to start on Friday, was extended on Wednesday by an additional week until June 29 after a "cyberattack" threatened to derail it.
The website has received billions of hits since last Saturday, including more than 10 billion in one 20-hour period, according to a statement from Robert Chung, director of the public opinion programme at Hong Kong University who is responsible for the referendum's website.
Such massive scale hits are known in computing as distributed denial-of-service attacks, which aim to overwhelm a website with requests so regular visitors can't reach it.
The referendum website was operating normally on Thursday. Voters will also have the option to cast ballots at 15 voting stations throughout Hong Kong on two consecutive Sundays.
Despite the attack, roughly 35,000 people participated in pre-registration and a mock vote on Wednesday.
"As I see it, we are under such serious attack it exactly shows that Beijing is taking us seriously," law professor Tai said.
The website of Apple Daily, a local tabloid known for its pro-democracy leanings, was also attacked on Wednesday, taking more than 40 million hits a second during the peak. The newspaper quoted its owner, Jimmy Lai, as calling the Chinese Communist Party the "backstage manipulator" behind the attack. Lai is persona non grata in China, from which he fled at the age of 12, smuggled by boat into Hong Kong.
Chinese and Hong Kong officials, editorials in pro-Beijing newspapers and businessmen have in recent weeks strongly criticised Occupy Central, which plans mass protests in the Central business district this summer, saying it will harm Hong Kong.
"We are using the civil referendum to tell Beijing what is our baseline, that is true democracy must be something allowing electors to have genuine choices," Tai said.
Hong Kong returned to China with wide-ranging autonomy under the formula of "one country, two systems" - along with an undated promise of full democracy, an issue never broached by the British until the dying days of 150 years of colonial rule.
The summer protests could see more activist groups spill on to the streets as political tensions rise. Already last week, the city's normally peaceful protests took on a violent edge.
On Friday, a group of radical protesters tried storming their way into the Legislative Council, smashing glass and ramming doors with steel barricades and bamboo poles.
Tai stressed his movement hadn't yet decided on an exact date to launch the street protests, though the results of the referendum would have a strong bearing.
"IT ONLY HURTS HONG KONG"
Rita Fan, a senior Hong Kong delegate to China's parliament, the National People's Congress, said the Occupy protests would hurt Hong Kong and stoke Beijing's mistrust of the city.
"I understand from listening to various people who are officials from the mainland that they do not wish to see this happen, but they are not afraid if it happens," Fan told Reuters.
"It only hurts Hong Kong ... If the Hong Kong police force is unable to contain the situation then the international ratings agencies may consider that Hong Kong is politically not stable and that may affect our rating."
A Hong Kong police source told Reuters that mainland law enforcement officials had stepped up liaison work with police over the past year, forming an informal working group on how to tackle the protests.
A police spokesman gave no immediate response, but stressed the force could deal with any "internal security incidents".
Banks in Central have been holding emergency drills and contingency planning for possible disruptions to operations. [ID:nL4N0OT1JR]
Several current and retired Chinese officials have warned in recent months, however, that China is prepared to unleash the People's Liberation Army (PLA) garrison to handle riots in Hong Kong – a prospect dismissed by some analysts.
"Disorder that is too intense for the Hong Kong police to handle could justify deployment of the PLA to restore stability," wrote Hong Kong-based risk consultancy, Steve Vickers and Associates, in a report. "Such a scenario is unlikely, but would present a major threat to businesses and to Hong Kong's autonomy and reputation."
(Additional reporting by Adam Rose and James Zhang; Editing by Nick Macfie and Jeremy Laurence)