US lawmakers have approved new Hong Kong-related sanctions, after Beijing imposed a security law that has been widely condemned across the world. The US measure, which penalises banks which do business with Chinese officials, was passed unanimously by both the House and the Senate. It has been sent to President Donald Trump to sign into law. Critics say China's law ends freedoms guaranteed for 50 years after British rule ended in Hong Kong in 1997. "The law is a brutal, sweeping crackdown against the people of Hong Kong, intended to destroy the freedoms they were promised," said House Speaker Nancy Pelosi. UK Prime Minister Boris Johnson said the passing of the law was a "clear and serious breach" of the 1985 Sino-British joint declaration. Under this declaration, Hong Kong was handed back to China in 1997, with certain freedoms guaranteed for at least 50 years under the "one country, two systems" agreement. The UK has offered residency, and then citizenship, to up to three million Hong Kongers. But on Thursday China threatened "corresponding measures" to block the citizenship plan. "If the British side makes unilateral changes to the relevant practice, it will breach its own position and pledges, as well as international law and basic norms," said the Chinese Embassy in the UK. Meanwhile, a 24-year-old man from Hong Kong - suspected of stabbing a police officer during Wednesday's protests - has been arrested on a plane while trying to flee to London. The suspect, known only as Mr Wong, was detained on the plane moments before it set off. China said the security law was necessary to stop the type of protests seen in Hong Kong during much of 2019. And despite widespread international condemnation from leading powers, more than 50 countries, led by Cuba, supported China at the UN this week.