To the sound of whirring clippers, Hong Kong democracy activists shaved their heads Tuesday in a symbolic act of protest against China's increased political control over the city.

Dozens of pro-democracy campaigners gathered in a church hall packed with supporters and press for the ritual, declaring that the removal of their hair represented their willingness to make sacrifices for Hong Kong's political future.

Among those who had their heads shorn were the three founders of Occupy Central -- a grassroots network which has vowed to take over the streets of the city's financial district following China's recent decision to restrict who can stand for the city's top post.

"It is our determination to show we can give something up in order to fight for something more important," said Benny Tai, an Occupy co-founder and local academic.

"To Chinese people, our hair is a gift given to us by our parents. It is precious. One day we will also give up our freedom to fight for democracy," he added.

The words "hair" and "law" sound similar in both Mandarin and Cantonese and dissidents have used head-shaving in the past to mock what they regard as China's limited rule of law.

Activists in the former British colony had their hopes for genuine democracy dashed after China announced last week that candidates for the city's next leader in 2017 would be vetted by a pro-Beijing committee and that only two or three people would be allowed to stand.

A coalition of pro-democracy groups, led by Occupy Central, have labelled the restrictions a "fake democracy" and vowed to usher in a new "era of civil disobedience" against the decision.

But the movement has recently lost some steam, with its senior leaders in the semi-autonomous Chinese city stepping back from their shriller rhetoric and questioning their ability to change Beijing's mind.

- Recapture momentum -

In a downbeat interview last week, Tai even admitted that support for his movement might be waning -- a claim that both he and other senior members of the Occupy movement later backtracked on.

Activists are trying to recapture some of the anger and enthusiasm that was apparent 10 days ago when thousands gathered in a public park vowing to fight Beijing's increasing political control over the city with peaceful direct action.

During Tuesday's ceremony Tai and two fellow Occupy founders shaved their heads first as a sombre cello rendition of Beethoven's "Ode to Joy" played in the background.

Forty supporters from a range of pro-democracy groups followed suit to loud applause.

Tanya Chan, a former lawmaker and Civic Party member, was one of those who volunteered to lose her locks.

"I don't know what I look like now as I have never done that before," she joked, adding: "I believe our road to democracy is long but we have companions along the way."

Outside the venue several anti-Occupy supporters heckled democracy activists. One man sparked a brief scuffle in which a woman was knocked to the ground.

Police later said that three men and one woman, aged between 18 and 38, had been arrested for common assault in relation to that incident, following a complaint by the victim.

The 29-year-old, who was working as a volunteer at the venue, said she had been "pushed" to the ground, police added.

Britain handed Hong Kong back to China on July 1, 1997 under a "one country, two systems" agreement which allows civil liberties not seen on the mainland, including free speech and the right to protest.

But public discontent is rising over political interference, increasing inequality and the perceived cosy relationship between the city's powerful business elite and Beijing.

Hong Kong's vocal dissident community has previously used public acts of head shaving to protest against the mainland government.

In February pro-democracy activists including local lawmakers shaved their heads over the continued incarceration of Nobel Peace Prize winner Liu Xiaobo and the house arrest of his wife Liu Xia on the Chinese mainland.