(Bloomberg) -- Hong Kong police said protesters attempted to block roads and disrupt traffic early Wednesday morning, ahead of what could be the biggest day of demonstrations in months against China’s moves to increase control of the city.

Officers were clearing roadblocks in multiple areas after a group of “thugs” sought to disrupt traffic with nails and other debris, police said in a statement posted to Facebook. The force warned commuters to check traffic conditions before heading out. Main thoroughfares in the city were largely fine.

“The police warn the mob to stop illegal activities immediately, otherwise they will be arrested,” it said.

Protests are planned for Wednesday near the Legislative Council building in central Hong Kong, where lawmakers plan to hold a hearing on a bill that would criminalize disrespect toward China’s national anthem. They are also fighting against China’s plans to impose a national security law that opponents fear will curtail essential freedoms and criticism of the Communist Party.

The U.S. is mulling ways to respond to China’s moves, which Secretary of State Michael Pompeo called a “death knell” for the high degree of autonomy that Beijing promised to Hong Kong ahead of taking control from Britain in 1997. That could include a range of sanctions against Chinese officials and businesses, according to people familiar with the matter.

U.S. Mulls Sanctions on Chinese Officials, Firms Over Hong Kong

The Hong Kong Confederation of Trade Unions, which represents 145,000 members, has called for a general strike on Wednesday. More than a dozen high school student groups have also issued a joint statement urging their peers -- newly returned to campuses following months of closures induced by the coronavirus -- to strike.

The Communist Party “is blatantly targeting Hong Kong people’s revolution in the past year, spelling an end to the people’s democratic autonomy and freedom of expression,” they said in the statement, which was shared on the Facebook page of leading activist Joshua Wong’s pro-democracy group, Demosisto. “Hong Kong students will not be able to speak freely in the future and instead be scrutinized for every word and be at risk of incarceration.”

Hong Kong’s police force has readied 3,500 riot officers in anticipation of the protests, local Cable TV reported, citing unidentified people. Television footage showed newly added metal and water-filled barricades near the city’s legislature, Central Government Offices and People’s Liberation Army garrison building.

‘Free Society’

China last week announced it would bypass Hong Kong’s legislature to implement national security legislation banning subversion, secession, terrorism and foreign interference in the former British colony. Key details about the proposed laws remain unclear.

Reuters, citing unidentified people familiar with the matter, said Tuesday the legislation is set to block foreign judges in Hong Kong from handling national security trials. Central and city government security agencies would also set up in Hong Kong as part of the legislation, which is subject to change and expected before Hong Kong legislative elections in September, the report said.

Despite criticism from foreign governments, Chief Executive Carrie Lam defended the security laws Tuesday, asserting that local residents supported them. She said it was untrue that the new measures would ban street protests or calls for her dismissal, and pledged that Hong Kong’s freedoms would be preserved. She said earlier this month that the anthem bill would get priority in the city’s legislature.

“We are a very free society, so for the time being, people have the freedom to say whatever they want to say,” she told reporters. “Hong Kong’s vibrancy and core values in terms of the rule of law, the independence of the judiciary, the various rights and freedoms enjoyed by people will continue to be there.”

The announcement of the legislation last week rattled markets, prompting business groups to seek clarification on whether the laws would erode Hong Kong’s competitive advantage from the mainland. It also brought protesters back on the streets Sunday for one of the largest protests in recent months, with riot police firing tear gas at demonstrators in a central shopping area in scenes reminiscent of last year’s unrest.

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