Hong Kong's leader hit back Tuesday at Chinese media criticism of an unofficial democracy poll in the city, softening his previous stance on the ballot after turnout far exceeded organisers' expectations.

More than 700,000 people have voted so far in the informal referendum, as fears grow that Beijing will backtrack on its promise to allow Hong Kong's voters to choose the leader they want.

Hong Kong's chief executive Leung Chun-ying said Tuesday that voters had "expressed their hopes and demands" for elections of the city's leader in 2017.

He hit back at an editorial in China's state-run Global Times newspaper condemning the poll as "an illegal farce" and saying that China's massive 1.3 billion population outweighed opinions in Hong Kong.

"Global Times yesterday came out with a piece, headlined: 'However many involved in illegal referendum, it can't match 1.3 billion' -- I don't agree with that," Leung said.

"Nobody should place Hong Kong people in confrontation with mainland Chinese citizens," he added.

He also defended voters' rights to have their say.

"Many of the participating citizens have expressed their hopes and demands for the 2017 chief executive elections," he told reporters.

As of 2 pm local time (0600 GMT) Tuesday, more than 732,000 people had taken part online, via mobile phones and at polling stations.

The informal referendum, organised by pro-democracy activists, sets out three options for choosing the chief executive, all of which include civil nomination of candidates.

Currently the leader is chosen by a pro-Beijing election committee.

Leung's response contrasted sharply with his initial reaction, which was in line with Beijing's stance that the referendum proposals go against Hong Kong's constitution.

"All three options in the ballot are against the Basic Law," Leung said Friday, referring to Hong Kong's constitution, shortly after after the 10-day poll opened.

He made no mention of the legality of the proposals Tuesday.

But when asked by reporters, Leung rebuffed Beijing's earlier criticisms that holding the referendum was illegal.

"In our language, it (the referendum) does not have any legal basis, but it will not lead to criminal responsibilities," he said.

- Caught in the crossfire -

"Leung's remarks demonstrate the fact that the Hong Kong government is politically sandwiched between Beijing and the people of Hong Kong who demand to select a chief executive through universal suffrage," Sonny Lo, head of Social Sciences at the Hong Kong Institute of Education, told AFP.

"It is the predicament of the Hong Kong government, being hard-pressed by the democrats while Beijing has already said 'no'."

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.

Occupy leader Benny Tai has called for those taking part in the poll to join a rally on July 1 -- traditionally a day when citizens protest on an array of issues.

However he told local news channel RTHK that it would be "unreasonable" to try to occupy the centre of the city on July 1 as it would not give the government enough time to respond to the poll, which ends June 29.

The Global Times again criticised activists Tuesday in its third editorial on the referendum in the past four days.

"The radicals in Hong Kong are dragging Hong Kong to a murky future," it said.

"China is not Ukraine and Hong Kong is unlikely to become another Kiev or Donetsk. However it is the power of Beijing that ensures its prosperity and stable political development."

Concerns over Chinese influence were exacerbated earlier this month after a white paper in which Beijing reasserted its authority over the semi-autonomous Chinese city.

Under the "one country, two systems" agreement, reached when the city of seven million people was handed over from Britain to Communist-ruled China in 1997, Hong Kong has guaranteed civil liberties not enjoyed on the mainland, including free speech and the right to protest.