Joshua Wong, the teenage face of Hong Kong's pro-democracy movement, said Saturday he has ended a four-day hunger strike designed to force the government into further talks on political reform.

"Under the strong urging of the doctor, I have stopped the hunger strike," Wong, who had not eaten in 108 hours, said on his Facebook and Twitter feeds.

The 18-year-old said he felt "extreme physical discomfort, dizziness and weakness in the limbs".

"Even if I stop the hunger strike, it doesn't mean that the Hong Kong government can ignore our demands," Wong said.

Wong and two young female members of his Scholarism student group announced the "indefinite" hunger strike following one of the worst nights of violence at the demonstrations last Sunday.

Wong's latest announcement came after fellow hunger striker Isabella Lo said she would stop the hunger strike on Friday.

Scholarism said the hunger strike was still ongoing after two more people joined the action.

But in another blow late Saturday it, the group confirmed another hunger striker, 17-year-old Prince Wong, had been sent to the hospital late Saturday on the advice of their doctor.

News footage from TVB News showed an exhausted Wong, a secondary school student who joined the hunger strike with Joshua Wong and Lo on Monday, being stretchered onto an ambulance.

Earlier television news footage showed a weak-looking Joshua Wong being wheeled around the main protest site in Admiralty in a wheelchair.

He and other students on the hunger strike had been camping in tents near the city's government headquarters during the past week in an attempt to push the government to restart the political reform process.

Over 1,000 people joined a rally on Saturday night in the Admiralty protest site to show their support for Wong and other students.

- New methods of civil disobedience -

Student-led demonstrators are demanding free leadership elections for the semi-autonomous Chinese city, with the main protest camp continuing to block a long stretch of a multi-lane highway in central Hong Kong.

China's communist authorities insist that candidates for the 2017 vote must be vetted by a loyalist committee, which the protesters say will ensure the election of a pro-Beijing stooge.

Wong, who is in the running to be named TIME magazine's person of the year, called on Hong Kong authorities to reopen stalled talks with students.

Before Wong called off the strike, the government said it would not allow a hunger strike to affect its decision making.

"As a government we won't accept any illegal actions...or actions like a hunger strike to convince us to make any concessions," Secretary for Constitutional and Mainland Affairs Raymond Tam told reporters.

"To restart the political reform process...this demand is unrealistic," the city's chief secretary Carrie Lam told reporters.

The rallies for fully free leadership elections, which are in its third month, drew tens of thousands at their height, but numbers have dwindled as public support for the movement has waned.

One prominent protest leader said the students would decide "within a week" whether to leave two remaining camps in the centre of the southern Chinese city after authorities cleared a third last week.

Benny Tai, a founder of the pro-democracy movement branded the occupation of the city's main roads as "high-risk" Friday, urging protesters to turn to new methods of civil disobedience to push for electoral reform.