Some 100,000 people are expected to participate in a protest march against the Hong Kong government's plan to pass controversial anti-subversion laws next week.
"We have revised our application to the police and told them of our latest estimate that some 100,000 people are expected to attend the protest march," to the government headquarters on July 1, said Tsoi Yiu-cheong, spokesman for the Civil Human Rights Front.
"This is just our latest estimate from the 50,000 people we originally estimated," he said Friday.
"The most important task now is to get more people to join the march against the legislation of the anti-subversion law which could deprive us of our freedom," said Tsoi.
The Democratic Party chairman Yeung Sum and 10 other members started a 100-hour hunger strike that will end an hour before the mass protest on July 1.
"The fast is to show our anger" over the legislation of the anti-subversion bill, Yeung told reporters.
Accusing the government of ignoring public opinion and of rushing to enact the controversial law, Yeung said the fast was also meant to call on people to participate in the massive protest march next week.
The demonstration is timed to coincide with celebrations marking the former British colony's reversion to Chinese sovereignty in 1997.
Hong Kong is required under the Basic Law, the city's mini-constitution, to pass legislation banning treason, sedition, subversion and theft of state secrets.
Rights activists and pro-democracy groups have said they fear China could use the new law to suppress freedoms, including those of the media, speech and religion.
Meanwhile, the United States House of Representatives on Friday passed a resolution urging the Hong Kong government to withdraw its national security bill. It was approved by 426 votes to one, local radio reported.
However, Chief Executive Tung Chee-hwa told reporters that while authorities here respected the opinion of the US congress, the city had a constitutional duty to pass the laws.
Tung reiterated the government would explain to the international community why the territory needed to enact the legislation.
"The enactment of the law to protect the national interest of China is our constitutional duty ... but I want to emphasise this will not affect freedoms or the way of life.
"We are going to explain to our friends overseas what is happening here in Hong Kong, and having listened to us I am sure they will know what we are trying to do," said Tung.
There is mounting fear the law banning treason, sedition, theft of state secrets and subversion could stifle freedom of speech and strangle the free flow of information.
Chinese Premier Wen Jiabao is expected to visit Hong Kong from June 29 to July 1 to attend the handover celebration.
During his visit, Wen will attend the signing ceremony of the city's first free trade agreement with China as part of Beijing's support to help revive Hong Kong's economy.
The premier will be spared any glimpse of the protest which will be held hours after he leaves Hong Kong on July 1.