Hong Kong police have suspended seven police officers over the alleged beating of a pro-democracy protester as the city leader said he is ready to hold talks with the demonstrators.

The disciplinary measure came after video footage emerged depicting plain-clothed policemen shovelling a handcuffed protester around a dark corner, kicking him on the ground and repeatedly punching him.

Police public relations bureau senior superintendent Kong Man-keung said it took authorities more than 24 hours to identify all the officers that allegedly participated in the beating of Ken Tsang, a democracy activist and member of the Civic Party, the South China Morning Post reported.

The video of the incident broadcast by television network TVB sparked public anger and drew the condemnation of international rights groups.

Meanwhile Chief Executive Leung Chun-ying offered protest leaders the chance to sit at the negotiations table, although he warned China is not to bow to their demands.

"As long as students or other sectors in Hong Kong are prepared to focus on this issue, yes we are ready, we are prepared to start the dialogue," he told reporters. "This is why over the past few days ... we expressed the wish to students that we'd like to start the dialogue to discuss universal suffrage as soon as we can, and hopefully within the following week."

Protests in favour of democratic reforms in the former British colony started in September after Beijing decided that it was to screen candidates for the first election in the territory in 2017.

Leung stressed that Beijing's position is not likely to change although he said it might be possible to discuss the composition of the committee tasked with clearing candidates to run for chief executive.

"In the second round of consultation, we can still listen to everyone's views. There is still room to discuss issues including the exact formation of the nomination committee," he said.