London CNN —Several anti-monarchy protesters were arrested in central London ahead of the coronation of King Charles III on Saturday, their group has said, as the Metropolitan Police force faces scrutiny for its approach toward demonstrators at the historic event. Thousands gathered in central London on Saturday to celebrate the once-in-a-generation event. Republic, Britain’s largest anti-monarchy group, told CNN that police – without providing any reason – arrested organizers of the anti-monarchy protest. Yara Nardi/WPA Pool/Getty ImagesThe Metropolitan Police confirmed several arrests had been made in central London. There are also plans for facial recognition technology to be used in central London, which has sparked criticism from human rights groups.