South Korea reported 113 new coronavirus cases on Saturday (Jul 25), the largest single-day increase in almost four months, and officials warned the upward trajectory could continue as people carrying the disease enter the country from abroad.

More than three-quarters of the latest reported infections were imported, the Korea Centres for Disease Control and Prevention (KCDC) said.

"Every day, we feel a sense of crisis that the COVID-19 pandemic may not have peaked yet," KCDC deputy director Kwon Jun-wook told a briefing.

South Korea has reported a total of 14,092 cases and 298 deaths from the pandemic. Saturday's 113 infections were the highest since Mar 31.

Around 16 per cent of all the country's infections have been imported, with around 70 per cent of those Korean nationals.

Two South Korean military aircraft arrived from Iraq on Friday, carrying 293 workers who were evacuated as cases swelled in that country.

Kwon said on Saturday that 71 of those people were infected with COVID-19 and a further 11 people were being re-examined.

"It’s likely that there will be similar cases like this Iraq case anywhere in the world, and (South Korea) will repeat the same measure, so we urge people to factor that in when looking at figures of the confirmed cases," Kwon said.

A large number of crew members on a Russian ship have also tested positive, Kwon said.