The rendition bill has generated unusually broad opposition, from normally pro-establishment business people and lawyers to students, pro-democracy figures and religious groups
China on Monday strongly backed the Hong Kong government on a controversial bill that would allow extraditions to the mainland, and voiced opposition to "outside interference" following a massive protest against the legislation.
Organisers said more than a million people marched against the law, bringing central Hong Kong to a standstill at the weekend as the semi-autonomous city's pro-Beijing government battles a major political crisis.
Critics of the proposed legislation say it would erode precious freedoms in the city, and leave dissidents at the mercy of Beijing's opaque justice system.
Beijing was unmoved by the protest, with foreign ministry spokesman Geng Shuang saying it "will continue to firmly support" the Hong Kong administration.
"Second, we firmly oppose any outside interference in the legislative affairs" of the city, he said at a regular press briefing, adding that "some countries have made some irresponsible remarks about the amendment."
Chinese state-run media earlier slammed the Hong Kong protest organisers for "collusion with the West", and pointed to meetings between Hong Kong opposition figures and senior US officials.
The Chinese-language edition of the nationalistic Global Times dismissed Sunday's mass demonstration, one of the biggest shows of public anger since Hong Kong was returned to Chinese rule in 1997.
"It is very noteworthy that some international forces have significantly strengthened their interaction with the Hong Kong opposition in recent months," the paper said, describing the exchanges as "collusion."
The editorial pointed to meetings between Hong Kong opposition figures and US Secretary of State Mike Pompeo, as well as House Speaker Nancy Pelosi.
Hong Kong's pro-Beijing chief executive Carrie Lam struck a defiant tone in the wake of the protest, refusing to scrap the extradition bill.
The law's opponents have called for another demonstration on Wednesday.
The English-language China Daily said in an editorial more than 700,000 people had backed the legislation through an online petition, "countering a protest by about 240,000 people" -- the more conservative attendance figure given by police.
"Unfortunately, some Hong Kong residents have been hoodwinked by the opposition camp and their foreign allies into supporting the anti-extradition campaign," the state-run paper said.
Geng also pointed to the petition in support of the bill.
Coverage of the protest was muted in mainland China, with the state broadcaster ignoring the protest on Sunday's main evening news.
The official Xinhua news agency's English-language service repeated the city administration's position on the law "in response to a public procession."
Searches for the demonstration on China's Twitter-like Weibo platform yielded no results, and instead showed older content about unrelated events.
A mainland student in China told AFP his WeChat social media account was suspended for two days after he posted a picture of the protest in a three-person group chat.
"I feel awful, it's my first time being blocked," said the student, who did not participate in the protest.
A 50-year agreement between Hong Kong's former colonial ruler, Britain, and China means the city is guaranteed freedoms of speech and assembly unseen on the Chinese mainland.
But activists and opposition politicians are increasingly warning that these liberties are being eroded as Beijing tightens its grip on the city.
The proposed law would allow extraditions to any country with which Hong Kong does not already have a treaty, including mainland China.
Supporters say the law is needed to stop the city becoming a safe haven for mainland fugitives, but critics fear Beijing would use the law to go after its opponents.