More than 780,000 voters in Hong Kong have cast their ballot on the last day of an unofficial referendum on electoral reforms, part of a civil campaign that has been branded illegal by local and mainland Chinese authorities.

The 10-day online voting wrapped up on Sunday days ahead of a pro-democracy protests planned by activists in the southern Chinese territory to ratchet up the pressure on authorities.

Every Chinese should have the right to vote. Although people can't do it in China, we can do it in Hong Kong. 

Fu, 90-year-old voter

Tensions are running high in the former British colony with upwards of 500,000 people expected to participate in the pro-democracy rally on Tuesday, the anniversary of Hong Kong's handover to China.

Organisers expect this year's march to be the largest since Britain returned the Asian financial centre in 1997, with Beijing promising direct elections for the city's leader in 2017.

Hong Kong's leader is currently appointed by a 1,200-strong pro-Beijing committee and residents are guaranteed civil liberties not enjoyed on the mainland, including free speech and the right to protest.

Turnout for the informal referendum, organised by pro-democracy activists, has exceeded expectations with about 50,000 people casting their vote at polling stations on one day alone.

"Every Chinese should have the right to vote," a 90-year-old voter, who only gave his surname as Fu, told the AFP news agency on Sunday morning.

"Although people can't do it in China, we can do it in Hong Kong," he added. 

Another voter, William Chu, said: "We should send a strong message to the government."

Another pro-Beijing group, Caring Hong Kong Power, marched through the busy shopping district of Causeway Bay carrying bright orange balloons and urging people not to vote, the Reuters news agency reported.

Cyber attack

Concerns are rising in Hong Kong that Chinese influence over the semi-autonomous city is increasing, and activists hope the high turnout will put a stronger case for reform.

Poll organiser Benny Tai said on Sunday that after stations close at 1300 GMT, counting will start and the results will be made known to the public in the coming days.

The poll allows residents to choose between three options on how the chief executive ballot should be carried out in three years' time - each of which would allow voters to choose candidates for the top job, and all therefore considered unacceptable by Beijing.

The referendum was organised by protest group Occupy Central, who say they will take over the streets of Hong Kong if the government does not include an element of civil nomination in the election for the city's leader.

The poll's high turnout came despite a major cyber attack that affected electronic voting. Organisers blamed it on Beijing. Earlier this month, Beijing released a white paper reasserting its authority over Hong Kong.

Source: Agencies