HONG KONG—Hong Kong police arrested at least three protesters on the anniversary of mass protests against an extradition bill involving China in 2019 that rocked the financial hub and eventually led to Beijing introducing its “national security law” that has stifled dissent in the city by making anti-government speech and organizing illegal. The protesters were arrested for disorderly conduct and failing to produce proof of identity, while at least 10 people were summoned for violating a ban on gatherings, police said, after protests in the Kowloon district of Mongkok and the chanting of slogans in breach of a National Security Law imposed last June. Some people blocked roads by placing rubbish bins and other objects in them, police said. “The police strongly condemn protectors’ acts endangering public health and safety,” police said in a post on Facebook shortly before midnight on Saturday. The three people arrested were male aged 15 …