Hong Kong (CNN) -- Seven Hong Kong police officers have been arrested for assault over an alleged case of police brutality at pro-democracy protests last month which shocked residents of the Chinese territory.

Footage of the alleged assault, taken by a TV crew at the city's main protest site in Admiralty on October 15, was widely disseminated online, sparking an outcry from the public, politicians and rights groups.

It appeared to show officers leading the man to a dark corner, where he was laid on the ground and repeatedly kicked and punched while others stood around, keeping watch.

The alleged victim was identified as Ken Tsang, a member of the Civic Party political group. He is also a social worker and a member of the 1,200 member election committee that chooses Hong Kong's leader. Photos were subsequently released by the Civic Party showing Tsang with a bruised face and welts on his back.
Protester Ken Tsang is led away by police ahead of an alleged assault on October 15.
Protester Ken Tsang is led away by police ahead of an alleged assault on October 15.
Tsang displays bruising to his face following an alleged police assault.
Tsang displays bruising to his face following an alleged police assault.
Tsang also sustained injuries to his back during the alleged assault.
Tsang also sustained injuries to his back during the alleged assault.

In a statement Wednesday announcing the arrests, police addressed criticism they had taken too long to act, saying they had not delayed the handling of the case. The statement said Tsang had failed to show up to an identification parade Wednesday.