"The extraterritorial application of Hong Kong's national security laws is a form of transnational repression that threatens US sovereignty and the human rights and fundamental freedoms of people all over the world," said Matthew Miller, the department's spokesperson.

Hong Kong police on Tuesday announced the bounties of HK$1 million (around $130,000) for information leading to the arrest of the six activists, who are accused of national security crimes.

Authorities also said they would cancel the passports of seven others for whom bounties had already been issued, including ex-lawmakers Ted Hui and Dennis Kwok, local media said.

Political dissent in Hong Kong has been quashed since Beijing imposed a sweeping national security law in 2020 after huge, sometimes violent pro-democracy protests the year before.

Many opposition figures fled abroad, while others have been arrested and sentenced to years in jail.

On Thursday, Washington condemned the new arrest warrants and bounties, noting that some affected activists were based in the United States.

"We reject the Hong Kong government's efforts to intimidate and silence individuals who choose to make the United States their home," said Miller in a statement.

"These actions demonstrate Hong Kong authorities' disregard for international norms and for the rights to freedom of expression and peaceful assembly."

The Hong Kong announcement this week was the third time authorities have offered rewards of HK$1 million for help capturing those alleged to have violated the southern Chinese city's national security laws.

The two previous rounds of bounties in July and December last year were met with intense criticism from rights groups and others.

Responding to past criticism, Hong Kong and China have railed against "interference" from foreign countries.