South Korea tightened social distancing curbs across most of the country to try to combat its worst ever outbreak of coronavirus after new Covid-19 cases on Tuesday soared past previous daily peaks to 1,615.

Amid growing concerns over the more contagious Delta variant and a stagnating vaccine rollout, the latest daily tally easily surpassed the previous record — last Friday's 1,378, Reuters reports.

Cluster infections have spread rapidly around the capital Seoul and neighbouring areas fuelled by the Delta variant, the Korea Disease Control and Prevention Agency said.

Prime Minister Kim Boo-kyum said from Thursday the government would tighten distancing rules across most of the country, with the exception of some southern regions, to Level 2 on the country's four level scale.

Under level 2, gatherings of more than eight people are banned, and restaurants and bars must close by midnight.