Political dissent in Hong Kong was effectively quashed by a sweeping national security law imposed by Beijing in 2020 after huge, sometimes violent protests the year before.

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

Hong Kong on Tuesday announced rewards of HK$1 million (around $130,000) for information leading to the arrest of six individuals now living abroad but accused by the city's authorities of national security crimes.

On Thursday, US State Department spokesperson Matthew Miller said "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".

China said Friday that the law's extraterritorial application "is entirely in line with international law and standard practices", accusing the United States of "abus(ing) the concept of national security".

"China is strongly dissatisfied and firmly opposes (this). Hong Kong affairs are purely China's internal affairs, and we do not tolerate interference and meddling by any external power," foreign ministry spokeswoman Mao Ning told a regular press briefing.

"We urge the US side to earnestly respect China's sovereignty and Hong Kong's laws, and stop supporting these anti-China figures who sow chaos in Hong Kong," she added.

- 'Intimidate and silence' -

Hong Kong's bounty announcement this week was the third time authorities have offered rewards of HK$1 million for help capturing those wanted on national security charges.

The two previous rounds -- in July and December last year -- also prompted criticism from the United States and other countries, as well as rights groups.

Miller said that some of the activists on the latest list 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," Miller said.

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

The bounties are seen as largely symbolic given that they are for people living in nations unlikely to extradite political activists to Hong Kong or China.

Those affected this round include 29-year-old Carmen Lau, a former district councillor now living in Britain, former pollster Chung Kim-wah and Victor Ho Leung-mau, a 69-year-old YouTuber now based in Canada.