Lau Wing-kei, deputy district commander of Airport District of the Hong Kong police, speaks during a media briefing in south China's Hong Kong, Sept. 6, 2019. The Hong Kong police said Friday that a total of 18 people have been arrested for unlawful assemblies and violent acts at the Hong Kong International Airport on Aug. 13 and Sept. 1. (Xinhua/Mao Siqian)