TAIPEI, Taiwan (AP) — Most access to a major city adjacent to Beijing was suspended Thursday as the government tried to contain an outbreak of the coronavirus's easily transmitted omicron variant ahead of next month's Winter Olympics in the Chinese capital.

Tianjin, a port and manufacturing center with 14 million people, is one of a half-dozen cities where the government is imposing lockdowns and other restrictions in response to outbreaks.

With the success of the Games and China's national dignity at stake, Beijing is doubling down on a "zero-tolerance" policy that has more than 20 million people under lockdown in Xi'an in the west and other cities. Some are barred from leaving their homes.

On Thursday, Tianjin suspended train, taxi, bus and ride-hailing services to other cities. Airline flights and high-speed train services were suspended earlier and highways closed. People leaving the city were required to present negative virus tests and receive special permission.

Trucks carrying food and medical will be allowed in but drivers were told to wear masks and take other steps to avoid transmitting the virus, according to a city government notice.

Automaker Volkswagen AG said it shut down two factories in Tianjin on Monday and employees have been tested twice. "We hope to resume production very soon," it said in a statement.

Tianjin conducted mass testing for a second time Wednesday. The government asked residents to wait at home until they receive a negative result.

Tianjin's proximity to Beijing makes the timing particularly fraught. During the Tokyo Olympics in July, Japan saw a widespread outbreak driven by the delta variant.

Despite that, the disruptions for people in Tianjin remain relatively light.

"Everything is fine, the supermarkets and restaurants, you can go to all normally," said Yu Xuan, who works at a university in Tianjin.

Wang Dacheng, another resident, said his father who has trouble walking was able to get tested in their apartment.

"Tianjin people are pretty optimistic. Everyone's been very calm and collected," Wang said.

Elsewhere, restrictions in Xi'an, a city of 14 million people, and the central province of Henan have prompted complaints people sequestered in their apartments were running out of food.

China has imposed sweeping restrictions on movement since early 2020.

That started with the then-unprecedented step of sealing off 11 million people in the central city Wuhan, where the virus was first detected, and other parts of surrounding Hubei province.

The government also has prohibited most foreign travelers from coming into China and uses digital surveillance to track members of the public.

The measures have kept the virus from spreading into a full-fledged national outbreak so far. The country's vaccination rate now tops 85%.

The task has become more critical as support staff for the Olympics arrive ahead of the Feb. 4 start of the Games.

"I think it truly is a critical juncture for China. Can it stave off omicron?" said Dali Yang, a Chinese politics expert at the University of Chicago.

China reported 124 domestically transmitted cases on Thursday, including 76 in Henan province and 41 in Tianjin.

Authorities have reported a total of 104,379 cases since the pandemic began and 4,636 deaths, a figure that hasn't changed in months.

Anti-disease measures around the Olympics are stricter than Tokyo's, which were mostly effective in stopping transmission,, said Kenji Shibuya, research director at the Tokyo Foundation for Policy Research and a public health expert.

Beijing faces a potentially bigger risk because the more contagious omicron variant has shown itself adept at evading vaccines.

Moreover, the lack of widespread outbreaks means the Chinese population is protected only by vaccines and not by antibodies produced by previous infections, said Dr. Vineeta Bal, an Indian immunologist.

"The Olympics would be the first trial," said Bal. Omicron "can easily travel in China."

The Olympics are being conducted under a "closed loop" system that is meant to cut off all contact between athletes, journalists, staff and officials and the outside world.

They will travel between hotels and competition venues in special vehicles. Anyone who leaves the sealed environment will be required to quarantine for three weeks.

Police say anyone involved in a collision with an Olympics vehicle should avoid contact with people on board and wait for a special team to handle the situation.

Such measures should be able to prevent the spread of the virus within the bubble, said Kei Saito, a virologist at the University of Tokyo. But outside, it could be a different story.

"Omicron is three to four times more transmissible than delta," said Saito. "I think it's almost impossible to control the spread of omicron."

Organizers are determined the Games will go on despite the global pandemic and controversies including a U.S.-led diplomatic boycott over accusations of human rights abuses against mostly Muslim minorities in China's northwest.

"The world is turning its eyes to China, and China is ready," said President Xi Jinping, who also is leader of the ruling Communist Party, during an inspection tour last week.

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Associated Press researcher Chen Si in Shanghai and AP Science Writer Aniruddha Ghosal in New Delhi contributed to this report.