Tianjin Centers for Disease Control and Prevention confirmed its first case of the Omicron coronavirus variant in the city — the first on the Chinese mainland. The patient, who was asymptomatic, came from a European country, said Gu Qing, the head of the center.

Gu declined to name the country. The person arrived on Dec 9.

Authorities identified the Omicron variant through genome sequencing of samples collected from the patient on Monday at a designated hospital.

The center confirmed that the infection was the Omicron variant B.1.1.529. It was re-confirmed by the Chinese Center for Disease Control and Prevention, according to Xinhua News Agency.

"A special team of doctors is assigned to the patient, who is now under treatment in a special area of Haihe Hospital," he said.

Passengers on the same airline as the infected carrier are under close quarantine.

"To date, we have not confirmed any other case or found an asymptomatic case among them," Gu said.

The city has also tightened its COVID-19 prevention measures in the port and airport areas, as well as hospitals, he said.

As of Monday, 28.39 million vaccinations had been provided to residents in Tianjin, including foreigners. Up to 94.9 percent of residents 12 years or older have been vaccinated.