A Hong Kong activist allegedly assaulted by police during last year's pro-democracy protests said Wednesday he would present his case to a United Nations torture hearing next week.

Footage of activist Ken Tsang being punched and kicked by police officers was beamed around the world at the height of the mass protests that brought parts of the southern Chinese city to a standstill last year.

The video, aired by local television network TVB, showed a group of men hauling a handcuffed Tsang to a dark corner in a public park. One man stood over Tsang punching him while three others repeatedly kicked him.

Seven police officers were charged with assault over the incident, while Tsang himself was also charged with attacking 11 police officers.

Tsang, 40, said he would present his case at a UN Committee Against Torture hearing in Geneva next Tuesday.

"Those seven policemen being accused should be charged with torture, not with common assault," Tsang told AFP.

"We want to raise more pressure on the government on how they are handling the case," Tsang said, adding that the charges were only brought a year after the incident.

Tsang has previously slammed allegations against him as "unreasonable and ridiculous", while the justice department has justified the assault charge against, saying he "splashed liquid from a plastic container" onto police.

Democratic Party chairwoman Emily Lau, who will also attend the UN torture hearing, told AFP: "On a number of occasions the police used force to deal with the peaceful demonstrators, and that is very, very unacceptable.

"They (Hong Kong government) don't want to be disgraced on an international stage... it is an important arena where Hong Kong is under international scrutiny," said Lau.

At the height of the 2014 protests, which lasted for 79 days, tens of thousands of people regularly gathered to demand political reform in a major challenge to China's communist rulers.

Thousands more joined the crowds after police fired tear gas in the afternoon of September 28, a move that shocked the public and galvanised the Umbrella Movement -- named after the umbrellas used to ward off sun, rain, tear gas and pepper spray.

The democracy protests began after China's central government said it would allow a popular vote for Hong Kong's leader in 2017, but insisted that candidates be vetted.

Hong Kong has been governed under a "one country, two systems" arrangement since it was handed back to China by Britain in 1997.