HONG KONG — Hundreds of riot police took up posts around Hong Kong's legislature overnight, as protests were expected on Wednesday (May 27) over a bill criminalising disrespect of China's national anthem and against plans by Beijing to impose national security laws.

The proposed new national security laws have triggered the first big street unrest in Hong Kong since last year, when violent protests posed Hong Kong's biggest crisis since the return of Chinese rule in 1997 from Britain.

Activists say the security laws could bring an end to the autonomy of China's freest city, now guaranteed under a policy known as "one country, two systems".

Diplomats, trade bodies and investors have also raised alarm. Thousands of protesters clashed with police on Sunday in the first big demonstrations since last year.

As he headed into the metro station next to the Legislative Council, known as Legco, 23-year-old Kevin said he was worried about what he called increasing Beijing assertiveness.

"The idea of one country, two systems is broken," he said after a late dinner at McDonald's. "China said it would stick to that agreement, but that’s not the case."

Authorities erected a wall made of two-metre-tall, white and blue plastic barriers filled with water around Legco, extending across a nearby park up to the picturesque Victoria Harbour.

Around midnight, riot police roamed the park, with squads stationed outside Legco and the neighbouring Central Government Offices building. Several police vans were parked on nearby roads.

In Washington, US President Donald Trump on Tuesday said the United States would announce before the end of the week a strong response to the planned security legislation for Hong Kong.

When asked at a news briefing if the response would include sanctions, he said: "No, it's something you're going to be hearing about ... before the end of the week, very powerfully I think."

Earlier, White House spokeswoman Kayleigh McEnany told a briefing that Mr Trump finds it "hard to see how Hong Kong can remain a financial hub if China takes over."

Mr Trump's economic adviser, Mr Larry Kudlow, said on Tuesday that China was making "a big mistake" with the planned security legislation and pledged the US government would pay expenses of American firms that wanted to shift operations from Hong Kong or China.

The anthem bill is set for a second reading on Wednesday and is expected to be turned into law next month. It requires China's "March of the Volunteers" to be taught in schools and sung by organisations, and imposes jail terms or fines on those who disrespect it.

Opponents say it represents another example of Beijing encroaching on Hong Kong, while supporters say the city has a duty to ensure national symbols are treated respectfully.

Hong Kong and Beijing authorities have issued repeated statements insisting there is no risk to the city's high degree of autonomy, urging patience until the laws are finalised.

Hong Kong police issued a warning late on Tuesday that they would not tolerate disruptions to public order, after activists circulated calls online for protests on Wednesday.

The security legislation could pave the way for mainland security agencies to open up branches in the global financial hub. It targets secession, subversion, terrorism and foreign interference — terms that are increasingly used by authorities to describe last year's pro-democracy protests. REUTERS