Suifenhe, Heilongjiang province, confirmed three cases of COVID-19 and nine asymptomatic cases on Tuesday, the city's Center for Disease Control and Prevention said.

The cases were found during tests launched across the city on Monday and were diagnosed as COVID-19 cases after expert consultation, the center said.

The people have been sent to a designated hospital for quarantine and treatment and all close contacts have been quarantined.

The city of Dongning, Heilongjiang, reported a confirmed case on Tuesday involving a person who had returned from Suifenhe. That case was also detected on Monday in citywide tests.

Dongning and Suifenhe are two port cities on the China-Russia border under the administration of Mudanjiang in Heilongjiang.