HONG KONG, July 30 (Reuters) - Hong Kong police said on Friday they had arrested a 40-year-old man for booing China"s national anthem in a shopping mall broadcasting live the city"s first Olympic gold medal win in 25 years earlier this week. More than 100 people gathered briefly on Monday night in a mall to watch on a wide screen Cheung Ka Long claiming the Olympic men"s individual fencing title. read more Police said they fielded complaints that some people booed during the award ceremony when China"s national anthem was played. Some shouted "We are Hong Kong," and clapped, according to video clips seen by Reuters. In a statement posted online, police said the arrested person had held a Hong Kong British colonial flag, booed and chanted slogans with others at the time. Police said his alleged aim was to "incite hatred and politicize sports", and that his conduct, taken as a whole, may have insulted the national anthem. The man identified himself as a journalist, police added. "The police have launched an investigation into the incident and will collect relevant evidence," police earlier told Reuters. Hong Kong passed a law in June 2020 that criminalised disrespect of China"s national anthem. Anyone found guilty of misusing or insulting the anthem could be jailed for up to three years and fined. Tensions in Hong Kong towards China peaked in 2019 with mass, pro-democracy protests against Beijing"s tightening grip on the city. Beijing later imposed a sweeping national security law that critics say has seriously undermined the former British colony"s autonomy and freedoms, including the right to protest. Monday"s shopping mall broadcast was a rare occasion for Hong Kong people to gather, with groups limited to a handful of people since early 2020 because of the coronavirus. Since the law took effect, most prominent pro-democracy politicians and activists have been charged, with some jailed. Others have into self-exile. Chinese and Hong Kong authorities say the law was vital to restore stability and deny such prosecutions are politically motivated.