Hong Kong leader Carrie Lam said she has to pile up cash at home as she has been unable to open a bank account in the global financial centre since Washington sanctioned her shortly after Beijing imposed a national security law on the city.

Beijing circumvented Hong Kong's legislature and imposed a national security law on the former British colony on June 30, a move condemned by some foreign governments, business groups and rights groups.

Hong Kong and authorities in Beijing said the law...