Ruili city in Southwest China's Yunnan province has classified three areas as high-risk for COVID-19, starting at 7 pm Monday, and six areas as medium-risk, according to information released at a news conference on Monday night.

Key groups at key areas in Ruili started taking serum antibody tests on Monday. All people in the city's urban districts will take the second round of nucleic acid tests starting at 8 am on Tuesday, Gong Yunzun, Party chief of Ruili, said at the news conference.

By Monday at 6 pm, the city had traced a total of 3,780 close contacts and 3,171 indirect contacts of confirmed or asymptomatic cases.

By 2 pm on Monday, a total of 126,358 doses of COVID-19 vaccines had been given in Ruili, with no serious side effects occurring, Gong said.

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

All the confirmed and asymptomatic cases were found in the border city of Ruili during a citywide nucleic acid testing campaign, the commission said.