China is set to impose new national security legislation on Hong Kong after last year's pro-democracy unrest, a Chinese official has said.
The move has already drawn a warning from US President Donald Trump that the United States would react "very strongly" against the attempt to gain more control over the former British colony.
China's action could spark fresh protests in Hong Kong, which enjoys many freedoms not allowed on the Chinese mainland, after often violent demonstrations of 2019 plunged the city into its deepest turmoil since it returned to China's rule in 1997.
Mr Trump, who has ratcheted up his anti-China rhetoric as he seeks re-election in November, told reporters at the White House that "nobody knows yet" the details of China's plan.
"If it happens we'll address that issue very strongly," Mr Trump said, without elaborating.
Pro-democracy demonstrators have for years opposed the idea of national security laws, arguing they could erode the city's high degree of autonomy, guaranteed under the "one country, two systems" formula in place for two decades.
"In light of the new circumstances and need, the National People's Congress is exercising its constitutional power" to establish a new legal framework and enforcement mechanism to safeguard national security in Hong Kong, Zhang Yesui, the spokesman for the Chinese legislature, said.
He spoke at a briefing on the eve of the start of China's annual parliamentary session. Further details would be given tomorrow, he said.
Hong Kong media outlets reported that the legislation would ban secession, foreign interference, terrorism and all seditious activities aimed at toppling the central government and any external interference in the financial hub.
The legislation, which will face NPC deliberations, could be a turning point for its freest and most international city, potentially triggering a revision of its special status in the US and likely to spark more unrest.
Online posts had already emerged urging people to gather to protest tonight and dozens were seen shouting pro-democracy slogans in a shopping mall as riot police stood nearby.
Opposition democrats said the move would gravely wound Hong Kong's reputation as a financial centre and its high degree of autonomy.
"If this move takes place, 'one country, two systems' will be officially erased," democratic politician Dennis Kwok said.
"This is the end of Hong Kong," Mr Kwok added, flanked by other opposition democrats.
Hong Kong people took to the streets last year to protest a now-withdrawn bill that would have allowed extraditions of criminal suspects to mainland China.
The movement broadened to include demands for broader democracy amid perceptions that China was tightening its grip over the city.
"If Beijing passes the law ... how (far) will civil society resist repressive laws? How much impact will it unleash on to Hong Kong as an international financial centre?" said Ming Sing, a political scientist at the Hong Kong University of Science and Technology.
The Hong Kong dollar weakened on the news.
A senior Hong Kong government official said details on the move and its implementation remained unclear.
The NPC annual session beginning tomorrow was delayed for months by the coronavirus.
Earlier this month US Secretary of State Mike Pompeo said he was delaying a report assessing whether Hong Kong was sufficiently autonomous to warrant US's special economic treatment that has helped it remain a world financial centre.
The delay was to account for any actions at the NPC, he said.
Tension between the two superpowers has heightened in recent weeks, as they exchanged accusations on the handling of the coronavirus pandemic, souring an already worsening relationship over trade.
A previous attempt by Hong Kong to introduce national security legislation, known as Article 23, in 2003 was met with mass peaceful protests and shelved.
