A total of 20 people had been aboard the vehicle as it made its way to the southeastern city of Ulsan -- which is still in recovery mode after being recently hit by heavy typhoon-related wind and flooding.

The bus crashed and caught fire late Thursday after suffering a burst tire on an expressway close to Ulsan shortly after 10 p.m. (1300GMT), according to local police.

Those who passed away had been trapped inside, while the survivors were treated for injuries and smoke inhalation based on the official account cited by Yonhap News Agency.

The majority of the passengers were retirees and spouses from South Korea's Hanwha Chemical Co.