Seven Hong Kong police officers have been arrested for assault over an alleged case of police brutality at pro-democracy protests last month. Footage taken by a TV crew at the city's main protest site in Admiralty on October 15 appeared to show officers leading a man to a dark corner, where he was lain 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. The footage was widely disseminated online, sparking an outcry from the public, politicians and rights groups. On Thursday, meanwhile, police pledged to keep the streets of Mong Kok open after the biggest operation in two months cleared encamped pro-democracy protesters. About 6,000 officers will be assigned to the district until November 30 to prevent reoccupation, the South China Morning Post reported.