South Korea has reported its biggest daily jump in Covid-19 cases in 70 days as the government began fining people who fail to wear masks in public.

The 191 cases added to the country’s caseload on Friday represented the sixth consecutive day of over 100 infections and the highest daily increase since September 4.

More than 120 of the cases were from the Seoul metropolitan area, where the coronavirus has spread in a variety of places, including hospitals, nursing homes, churches, schools, restaurants and offices.

The steady spread of the virus has alarmed government officials, who eased social distancing measures to the lowest level since October to soften the pandemic’s shock on the economy.

While this has allowed high-risk venues like nightclubs and karaoke bars to reopen, prime minister Chung Sye-kyun during a virus meeting on Friday said the viral spread could force the government to “seriously consider” tightening social distancing again.

“We are at a precarious situation,” he said, pleading for citizen vigilance and for labour unionists and civic groups to cancel planned rallies.

South Korea has so far weathered its outbreak without major lockdowns, relying on an aggressive test-and-quarantine program and relatively widespread use of masks among the public.

From Friday, officials started to impose fines of up to 100,000 won (£68) for people who fail to properly wear masks in public transport and a wide range of venues, including hospitals, nursing homes, pharmacies, nightclubs, karaoke bars, religious and sports facilities and at gatherings of more than 500 people.

People will also be required to wear masks at restaurants and cafes when they are not eating or drinking.

In the capital Seoul, city employees were deployed at subway stations and bus stops to monitor commuters. There were no immediate reports of major disruption.