KUNMING -- Ruili city in Southwest China's Yunnan province will launch the second round of nucleic acid testing that includes all residents of the city proper Tuesday.

The recent increase in COVID-19 cases and asymptomatic cases was mainly due to a new round of testing among key groups of people and people in high-risk areas on Saturday, said Gong Yunzun, Party chief of the city, at a press conference Monday.

The city reported 15 new locally-transmitted COVID-19 cases and five new asymptomatic cases on Sunday, the provincial health commission of Yunnan said on Monday.

It added three high-risk and three medium-risk areas for COVID-19 outbreak on Monday.

Dozens of locally-transmitted COVID-19 cases have been reported in the city since March 30. Local authorities launched a citywide nucleic acid testing drive on March 31 and urged residents to observe home quarantine.