South Korea has reported its highest daily rise in novel coronavirus cases since early March as outbreaks from churches around the capital spread, prompting a warning of a nationwide wave of infections.

The 297 new infections mark the sixth straight day of triple-digit increases in a country that has managed to blunt several previous outbreaks.

Nearly 90 per cent of the new cases appeared in the capital, Seoul, and surrounding areas, raising concern of the rapid spread of the virus in a metropolitan area of more than 25 million people.