The outbreak of the Omicron strain of COVID-19 has been effectively controlled in Tianjin, a senior official said on Friday. But relevant departments will not let their guard down, and residents, too, should not be careless, Gu Qing, deputy secretary general of Tianjin municipality, said at news conference.

According to Gu, who is also director of the Tianjin Municipal Health Commission, the northern port city reported eight locally transmitted confirmed cases on Thursday. "But all the patients have mild symptoms and are in quarantine," he said. No asymptomatic cases were found on Thursday.

By the end of Thursday, Tianjin had reported 348 confirmed cases and 22 asymptomatic ones. The city detected six positive cases in the fourth round of citywide nucleic acid testing that began at 6 am on Thursday; 12.5 million people were tested.

All the positive cases were detected among people in quarantine centers or sealed off areas.

More than 58 million people times had been tested in all four rounds of citywide nucleic acid tests in the past weeks. As of Friday noon, all the patients had only mild symptoms and three had been cured and discharged from hospitals.