Seoul (AFP) - A fire swept through a hospital in South Korea, killing 21 people and leaving six others in a critical condition, according to a report.

Most of the patients who died at the hospital in Janseong county, south of the capital Seoul, were in their seventies and eighties, Yonhap news agency said, citing police and fire officials.

Thirty bedridden patients were trapped by "choking fumes" on the second floor of an annex building, while 10 patients on the first floor managed to escape, the report said.

One nurse was on duty at the time and was among the dead.

It was the second deadly blaze in South Korea in two days after seven people were killed and 41 injured in a fire at a bus terminal near Seoul on Monday.