Hong Kong police came under fire on Wednesday after officers were filmed assaulting a protester, amid some of the most violent clashes since mass democracy rallies erupted two weeks ago.

The footage, broadcast on public television network TVB, showed officers beating and kicking a handcuffed and unarmed protester, sparking outrage and calls for prosecution from activists and lawmakers.

Prominent student leader Joshua Wong said trust between police and activists had hit an all-time low: "The proper action police should take is to bring the protester to the police car, not to take him away and then punch and kick him for four minutes," he told reporters.

The city's security chief said the accused officers had been "removed" from their posts after the assault that occurred when police swooped in to clear newly erected barricades near government headquarters.

"It is stomach-churning to think there are Hong Kong police officers that feel they are above the law," Mabel Au, director of Amnesty Hong Kong said in a statement.

"Any investigation into this incident must be carried out promptly and all individuals involved in unlawful acts must be prosecuted."

Protesters had blocked an underpass with concrete slabs and metal barricades

Violence intensifies

The assault came as police, armed with riot gear and pepper spray, moved early on Wednesday to clear Lung Wo Road, a major east-west arterial road near government headquarters that had been blocked by protesters. At least 45 people were detained for obstructing the police.

Hong Kong police later released a statement, saying that protesters "advancing against police cordon line even with their arms raised is not a peaceful act."

Wednesday saw some of the worst violence since the pro-democracy rallies began three weeks ago.

A recent decision by Beijing to vet all chief executive candidates for the 2017 elections angered many in Hong Kong, who are demanding the Chinese government reverse the law and give them universal suffrage. Supporters of the mass protest movement, led in large part by students, are also calling for the resignation of the current chief executive, Leung Chin-Ying.

Violence between security forces and protesters escalated on Wednesday

Pro-Beijing paper: 'stability is bliss'

On Wednesday, the front-page editorial of the Chinese Communist Party's newspaper, the People's Daily, accused the demonstrators of "exacerbating disorder and turmoil" and provoking "more severe illegal activities" by continuing their protests.

"Stability is bliss and turmoil brings havoc," the paper said, adding that the protesters were "doomed to fail."

The message reflected a similar statement by Hong Kong leader Leung Chun-ying, who has said there was "almost zero chance" that Beijing would change its rules for the 2017 vote.

glb/ng (AFP, Reuters)