HONG KONG (Reuters) - China said on Wednesday Hong Kong’s protest movement had reached “near terrorism” and more street clashes followed ugly scenes the previous day when protesters set upon men they suspected of being government sympathizers.

The United States said it was “deeply concerned” at news of Chinese paramilitary police movement near the border, urged Hong Kong’s government to respect freedom of speech, and issued a travel advisory urging caution when visiting the city.

By nightfall, police and protesters were again facing off on the streets, with riot officers shooting tear gas almost immediately as their response to demonstrators toughens.

Ten weeks of increasingly violent confrontation between police and protesters have plunged Hong Kong into its worst crisis since it reverted from British to Chinese rule in 1997.

Flights resumed on Wednesday amid heightened security at Hong Kong airport, one of the world’s busiest. This followed two days of disruptions sparked by protesters swarming the airport, where, late on Tuesday, they detained two men they suspected opposed them.

China’s Hong Kong and Macau Affairs Office in Beijing called the behavior at the airport no different to terrorism and said it must be severely punished.

“We’re deeply sorry about what happened yesterday,” read a banner held up by a group of a few dozen demonstrators in the airport arrivals hall in the morning.

“We were desperate and we made imperfect decisions. Please accept our apologies,” the banner said.

In chaotic scenes that would once have been unthinkable for Hong Kong, a peaceful sit-in at the airport turned violent late on Tuesday as protesters confronted and held a man they believed was an undercover Chinese agent.

Busloads of riot police arrived in response, clashing with furious demonstrators before withdrawing once the man was removed, and leaving the terminal briefly in control of activists who then briefly detained a reporter from China’s Global Times newspaper, a nationalistic tabloid run by the ruling Communist Party’s official People’s Daily.

It was not clear whether the scenes of violence might have eroded the broad support the movement has so far attracted in Hong Kong, a major financial hub. The protests have also hit the city’s faltering economy.

“We promise to reflect and to improve,” protesters said in one message distributed on social media app Telegram.

“Sorry we were too reckless ... we are only afraid of losing your support to the whole movement due to our mistake, and that you give up on fighting.”

There has been little sign of a letup in the protests, which began in opposition to a now-suspended bill that would have allowed the extradition of suspects for trial in mainland China, but have swelled into wider calls for democracy.

Hundreds attended a demonstration in the residential area of Sham Shui Po, where police arrived and quickly used tear gas after protesters pointed lasers at the police station.

‘SWORD OF THE LAW’

China used its strongest language yet after Tuesday’s incidents. The People’s Daily called for “using the sword of the law” to restore order, and mainland social media users lauded the detained reporter as a hero.

The U.S. State Department called for restraint, and a spokeswoman warned that continued erosion of Hong Kong’s autonomy put at risk the privileged status it enjoys under U.S. law.

Hong Kong returned from British to Chinese rule in 1997 under a “one country, two systems” formula that promised wide-ranging freedoms denied to citizens in mainland China, and it enjoys preferential U.S. treatment in trade and economics.

The U.S. spokeswoman reiterated a U.S. call for all sides to refrain from violence and said it was important for the Hong Kong government to respect “freedoms of speech and peaceful assembly” and for Beijing to adhere to its commitments.

Another U.S. official said Beijing had stationed large numbers of paramilitary People’s Armed Police (PAP) “near and further out from Hong Kong,” but there had been no sign they were moving toward the border.

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The U.S. official said it appeared to be an effort to intimidate the protesters, but the protests had yet to reach a level that would compel Beijing to send them in.

The Global Times reported on Monday that People’s Armed Police had been assembling in Shenzhen, a city bordering Hong Kong, “in advance of apparent large-scale exercises.”

It cited video it had obtained showing numerous armored personnel carriers (APCs), trucks and other vehicles on expressways heading in the direction of Shenzhen over the weekend. It noted that the role of the PAP was “dealing with rebellions, riots, serious violent and illegal incidents, terrorist attacks and other social security incidents.”

Satellite images made available to Reuters on Wednesday from Maxar Technologies showed dozens of vehicles, including what appeared to be APCs, at the Shenzhen Bay Sports Centre across from Hong Kong.

On Tuesday, U.S. President Donald Trump, who has been seeking a major deal to correct trade imbalances with China, described the Hong Kong situation as “tricky” but said he hoped it would work out for everybody, including China, and “for liberty” without anyone getting hurt or killed.

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China has accused the United States of having a hand in the protests and has denied a request for two U.S. Navy warships to visit Hong Kong in the coming weeks, U.S. officials said.

France urged Hong Kong authorities to renew dialogue with protesters to find a peaceful solution.

AIRPORT REOPENED

At Hong Kong airport, which was designed by renowned British architect Norman Foster, blood, debris and signs of the scuffle were scrubbed away during the night, and cleaners and protesters themselves removed anti-government posters from the walls.

Hong Kong carrier Cathay Pacific Airways 0293.HK said a total of 272 departures and arrivals had been canceled because of the disturbances, affecting more than 55,000 passengers.

China’s aviation regulator demanded last week that Cathay suspend personnel supporting protests in Hong Kong from staffing flights entering its airspace. On Wednesday, the carrier said it had fired two pilots.

Forward Keys, a flight data firm, said the crisis had driven a 4.7 percent fall in long-haul bookings to Hong Kong between June 16 and Aug. 9 compared with the same period last year.

“I think the local events clearly are having a profound impact, probably in ways that we haven’t necessarily clearly articulated yet,” Charles Li, chief executive of the Hong Kong Stock Exchange, told reporters on Wednesday.

Protesters vowed to press on.

“All the people here are very scared,” Ann, a 21-year-old teacher, told Reuters at the airport as she carefully took down anti-government posters, folding them for re-use.

“But we are more scared that we do not have our freedoms anymore, and so that is why we continue our protests,” she said.

“We feel that our ideas are bulletproof.”