HONG KONG - The United States has called for a "swift, transparent and complete" investigation into the beating of a handcuffed Hong Kong democracy protester by plainclothes police, as fresh street clashes broke out early Thursday.
Television footage of officers assaulting the unarmed protester in a dark corner of a public park has sparked outrage and calls for prosecution from activists and lawmakers in the city.
Tensions soared in the former British colony after the video went viral Wednesday, with protesters saying they had lost all faith in the police despite the accused officers being "removed" from their posts by city authorities.
The United States said it was "deeply concerned" by the police brutality reports.
"We encourage Hong Kong authorities to carry out a swift, transparent, and complete investigation into the incident," State Department spokeswoman Jen Psaki told reporters, urging the government to show restraint and protesters to remain peaceful.
The Asian financial hub has been rocked by mass rallies for much of the last fortnight calling for full democracy and causing significant disruption to a city usually known for its stability.
Protesters are angry at China's insistence that it vet candidates standing for election as the city's next leader in 2017, a proposal they have dubbed "fake democracy".
After weeks of largely ceding control to protesters at three main sites, police have begun probing demonstrator defences in the last few days, tearing down some barricades and sparking running battles.
But the city authorities face a major backlash after footage was aired showing officers kicking and beating a handcuffed protester in a public park during clashes early Wednesday.
"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.
The incident has become another public relations disaster for the police, who were severely criticised for firing tear gas on umbrella-wielding protesters on September 28 in a move that attracted worldwide attention.
Demonstrators have also accused officers of failing to come to their aid during several attacks by violent pro-government thugs.