BEIJING, May 16 (Reuters) - Mainland China reported 18 new COVID-19 infections on May 15, up from 14 a day earlier, the national health authority said on Sunday.

In its daily bulletin, the National Health Commission (NHC) said four of the new cases were local infections in the northeastern province of Liaoning. The rest originated overseas.

The authority has sent a working group to Liaoning to guide its COVID-19 control efforts, while schools and kindergartens in the Bayuquan district, in the province's Yingkou city, have been temporarily shut from Sunday, official news agency Xinhua said.

Shenyang, the provincial capital, reported one new local case in the first 12 hours of Sunday, Xinhua cited the provincial health commission as saying.

On Friday, the NHC reported China's first local transmissions in more than three weeks, with a patient surnamed Li, who travelled to Anhui from Liaoning, identified as the source.

Wu Zunyou, chief epidemiologist at the Chinese Center For Disease Control and Prevention, said the latest resurgence of COVID-19 infections in the country likely started from Yingkou, local media reported.

The number of new asymptomatic cases, which China does not classify as confirmed cases, was 19 on Saturday, down from 25 the previous day.

The total number of confirmed COVID-19 cases in mainland China now stands at 90,847, while the death toll remained at 4,636.

China carried out about 12.4 million vaccinations on Saturday, taking the total to 392.99 million, the authority said. (Reporting by Eve Wu and Kevin Yao; Editing by Chris Cushing and Jacqueline Wong)