The original founders of Hong Kong's pro-democracy Occupy movement tearfully announced Tuesday they would "surrender" by turning themselves in to police and urged protesters on the streets to retreat.

But frustrated demonstrators at the city's main protest site said they felt "abandoned" by the move.

The announcement came after hundreds of pro-democracy protesters clashed with police late Sunday, leaving dozens injured in one of the worst nights of violence since rallies began more than two months ago.

"As we prepare to surrender, we three urge the students to retreat -- to put down deep roots in the community and transform the movement," said Occupy Central leader Benny Tai.

Tai said he, along with the group's co-founders Chan Kin-man and Chu Yiu-ming, would surrender to police on Wednesday.

But protesters, who have blocked three major intersections since late September demanding free leadership elections for the semi-autonomous city, said they cannot leave until their demands have been met.

"They talk about retreat. It is a betrayal of what we have insisted on all along," said 24-year-old protester Raymond Tsang.

"We should not consider an end to the campaign until there is a solid achievement."

Teenage protest leader Joshua Wong paid tribute to Tai and said the student groups leading the so-called 'umbrella movement' would discuss Occupy's request.

"If Benny Tai did not publicise the idea of civil disobedience at the beginning, then there would be no umbrella movement today," said Wong, who began a hunger strike Monday in a last-ditch attempt to force the government into further talks.

- A 'watershed' moment -

Academics Tai and Chan, along with Baptist minister Chu, founded the Occupy Central civil disobedience group in early 2013 to push for political reforms, but have increasingly taken a backseat as more radical student groups came to the fore.

Tai praised the bravery of those at the frontline of the mass occupations and criticised the police as "out of control", but added that it was time for protesters to leave "this dangerous place".

"To surrender is not to fail -- it is a silent denunciation of a heartless government," Tai said.

While there is no specific warrant out for the founders' arrest, Hong Kong and Chinese authorities have consistently slammed the protests as illegal.

Tai said he did not know how police would respond to their surrender, but that the trio were prepared for any consequences.

He said the Occupy movement would now take a different approach to promoting its cause, including through education and a new social charter.

But experts say the students are unlikely to listen to the call for retreat.

"The students have always thought that they were the major protagonists of the movement and that Benny Tai and so forth have always been riding on their coat-tails," political analyst Willy Lam said.

But he added that this was nonetheless an important turning point in the movement.

"This will be a watershed -- the fact that they are surrendering themselves means that, for the Occupy people, they think that phase one of this civil disobedience movement is over... and they are now conserving their strength for phase two, whatever that may be."

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

The main protest camp continues to block a long stretch of a multi-lane highway in central Hong Kong's Admiralty district.

Violent clashes broke out there Sunday night in a fresh escalation of tensions, with officers firing pepper spray at angry students trying to surround government headquarters.

The city's leader Leung Chun-ying warned Monday that the "intolerable" protests will come to nothing and hinted that further police action may take place.

A British colony until 1997, Hong Kong enjoys civil liberties not seen on the Chinese mainland, including freedom of speech and the right to protest.

But fears have been growing that these freedoms are being eroded under Chinese rule.

In London, British lawmakers urged the former colonial power to take a tougher line with China in an emergency debate on Tuesday, after a group of them was refused visas to visit Hong Kong.

Chinese authorities have accused Britain of seeking to interfere in the protests.

Andrew Rosindell, a member of Prime Minister David Cameron's Conservative party, called for the Chinese ambassador to be summoned to explain, and described the visa ban as "nothing short of an outrage".

"Britain has to decide whether we tolerate and simply accept China's behaviour... or whether we're prepared to reconsider" the nature of the relationship, Rosindell added.

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