HONG KONG (AP) — The Latest on Hong Kong protests (all times local):

1:40 a.m.

President Donald Trump tweeted Tuesday that U.S. intelligence believes that the Chinese government is moving troops to its border with Hong Kong.

Trump also tweeted that "Everyone should be calm and safe!" He provided no additional details.

Riot police briefly clashed with pro-democracy protesters outside the Hong Kong Airport for the second day on Tuesday though calm returned to the airport in the early hours of Wednesday.

The airport disruptions are an escalation of a summer of demonstrations against what some in Hong Kong see as an increasing erosion of freedoms. The protests have in recent weeks turned to focus on police brutality against demonstrators.

Earlier Tuesday, Trump called the Hong Kong protests a "very tricky situation," saying he hopes no one is injured or killed.

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1:25 a.m.

Most protesters and police have left Hong Kong Airport after a second day of demonstrations that caused mass flight cancellations at the busy transport hub.

Calm returned to the airport in the early hours of Wednesday after riot police briefly clashed with pro-democracy protesters outside the building earlier Tuesday night. Officers armed with pepper spray and swinging batons briefly tried to enter the terminal, while protesters used luggage carts to barricade entrances.

Hundreds of flights were cancelled Tuesday and Monday and passengers have been forced to stay in the city while airlines tried to find other ways to get them to their destinations.

The airport disruptions are an escalation of a summer of demonstrations against what some in Hong Kong see as an increasing erosion of freedoms. The protests have in recent weeks turned to focus on police brutality against demonstrators.

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1:10 a.m.

China's diplomatic mission in Geneva is lashing out at the U.N. human rights office, accusing its spokesman of making a "wrongful statement" about protests in Hong Kong that "sends the wrong signal to the violent criminal offenders."

In an e-mail to reporters, the mission took issue with comments Tuesday by spokesman Rupert Colville, who expressed concerns about the "escalation of violence" and the firing of tear gas canisters by security forces into crowded areas.

The mission lamented how the demonstrations in Hong Kong "have recently taken a violent turn as some radical mobsters deliberately perpetuated violence ... Their behavior has nothing to do with peaceful demonstration."

It urged the human rights office to "stop interfering in the affairs of Hong Kong."

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12:50 a.m.

Emergency officials have taken an injured mainland Chinese man away from Hong Kong's airport after angry protesters who accused him of being a Chinese undercover agent tied up his hands and tried to beat him up.

The man was pictured with his hands bound with cable ties, lying in a fetal position on the ground surrounded by a crowd of protesters as demonstrations continued at the airport for a second day and turned tense late Tuesday. Some tried to kick and hit him while others tried to hold the crowd back. Protesters said they detained him because he wore a press vest and claimed to be a reporter, but a mainland Chinese ID card was found in his belongings.

The chaotic situation eventually ended when protesters allowed ambulance workers to take the man away on a stretcher.

Pro-democracy protesters have been sensitive to police infiltration after activists were arrested by officers dressed just like them. Police have acknowledged that they use decoy officers in some operations.

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11:45 p.m.

Chaos has broken out at Hong Kong's airport as riot police move into the terminal to confront protesters who shut down operations at the busy transport hub for two straight days.

Officers armed with pepper spray and swinging batons clashed with protesters who used luggage carts to barricade entrances to the airport terminal on Tuesday night.

Police took several people into a police van waiting at the entrance to the airport's arrivals hall.

Police said they tried to help ambulance officers reach an injured man whom protesters had detained on suspicion of being an undercover agent.

Protesters also detained a second man whom they suspected of being an undercover agent. After emptying out his belongings, they found a blue T-shirt that has been worn by pro-Beijing supporters that they said was evidence he was a spy.

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7 p.m.

At least three concerts by overseas performers have been canceled in Hong Kong as protesters forced the city's airport to suspend operations for a second day.

K-pop star Kang Daniel and Scottish band CHVRCHES both announced Tuesday that they are calling off upcoming events. American singer-songwriter Alec Benjamin canceled an upcoming concert late Monday.

Kang's management office said the cancellation of a fan meeting scheduled for Sunday was because of safety concerns related to the protests, while CHVRCHES blamed "unforeseen circumstances."

The airport protests are the latest escalation in a summer of demonstrations aimed at what many in Hong Kong see as an increasing erosion of their freedoms.

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6:35 p.m.

The United Nations' top human rights official has condemned violence in Hong Kong's pro-democracy protests and called on the authorities and protesters to solve their dispute peacefully.

A spokesman for U.N. High Commissioner for Human Rights Michelle Bachelet said she was concerned by the recent "escalation of violence."

Rupert Colville said the UN Human Rights Office had also reviewed credible evidence that police are using "less-lethal weapons in ways that are prohibited by international norms."

Tactics by Hong Kong police have become a major issue for protesters.

The rights office urged Hong Kong authorities to investigate examples of officers firing tear gas canisters into crowded, enclosed areas and directly at individual protesters.

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5:45 p.m.

Hong Kong's airport has cancelled all remaining departing flights for the second day after protesters took over the terminals.

The airport authority announced early Tuesday evening that check-in services for departing flights were suspended as of 4:30 p.m. Other departing flights that have completed the process will continue to operate.

It said it did not expect arriving flights to be affected, though dozens of arriving flights were already cancelled.

The authority advised the public not to come to the airport.

Some flights were able to depart and land earlier Tuesday, a day after more than 200 flights were canceled.

The airport's arrival and departure halls were blocked by thousands of protesters who were gathered in the airport for the fifth consecutive day. They are calling for democratic reforms and an independent inquiry into alleged police brutality.

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4 p.m.

Thousands of protesters have returned to the Hong Kong airport and are once more threatening regular airline operations just one day after they prompted a full shutdown of one of the world's busiest transit hubs.

After filling up the arrivals hall, demonstrators are now streaming into the departures area despite increased security measures designed to keep them out.

The black-clad protesters held up signs to appeal to travelers from mainland China and other parts of the world. "Democracy is a good thing," said one sign in Simplified Chinese characters, which are used in mainland China instead of the Traditional Chinese script of Hong Kong.

One entrance to the immigration area was entirely blocked by protesters and arriving passengers struggled to get through.

More than 100 flights were cancelled as of Tuesday afternoon. Some flights were taking off and going through check-in as airlines worked through the backlog.

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2:45 p.m.

Flights have been taking off from the Hong Kong airport as it works through a backlog of cancelled flights while a few thousand protesters have once again occupied the arrival hall.

Some flights Tuesday were still cancelled. It was not immediately clear whether they were affected by the current demonstration, as occurred Monday, when about 200 flights were cancelled and airport completely shut down amid a mass protest.

The airport authority said they were implementing flight rescheduling Tuesday. The authority urged passengers "to use public transportation and allow sufficient time to go to the airport."

Hong Kong has seen two months of anti-government demonstrations that have increasingly impacted day-to-day operations in the financial hub.

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10:30 a.m.

Hong Kong leader Carrie Lam has defended law enforcement actions after protesters prompted an airport shutdown with calls to investigate alleged police brutality.

Airlines early Tuesday were checking in passengers for flights, including those cancelled the previous day because thousands of pro-democracy demonstrators had packed into the airport's main terminal.

Demonstrators have called for an independent inquiry into what they call the police's abuse of power and negligence. Some protesters thrown bricks, eggs and flaming objects at police stations.

Lam told reporters that dialogue would only begin when the violence stopped. She reiterated her support for the police and said they have had to make on-the-spot decisions under difficult circumstances, using "the lowest level of force."

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8 a.m.

One of the world's busiest airports was struggling to reopen the morning after thousands of pro-democracy demonstrators crowded into Hong Kong's main terminal and forced flight cancellations.

Passengers were checking in for flights Tuesday morning in a sign operations were returning to normal, although protesters have shown no sign of letting up on their campaign to force Chief Executive Carrie Lam's administration to respond to their demands.

About 200 flights had been canceled.

Passengers unable to leave on Monday were among those crowding in the departure hall.