At least 37 people have been killed and more than 70 injured in a fire at a hospital in southern South Korea.

The fire started on Friday morning at around 7:30am local time in the emergency room on the first floor of Sejong Hospital, Miryang, some 400km from the capital Seoul.

It was extinguished in three hours.

Firefighters expect the number of casualties will rise further, according to South Korea's official news agency, Yonhap.

At least nine people were seriously wounded in the blaze, Yonhap reported, adding that the fire was South Korea's deadliest in a decade.

The majority of those who lost their lives died of suffocation from toxic smoke, as opposed to burns.

Local media reported that a doctor and two nurses were among the dead. Most of the victims were believed to have been elderly patients, according to Korea Times.

The chief of Miryang City's fire department said that the hospital did not have fire sprinklers, the English-language Korean daily reported.

"There was so much smoke that it was hard for people to approach [the building]," a witness told a local television news outlet. "Even from 10 metres away, it was frightening."

Al Jazeera's Cathy Novak, reporting from Seoul, said President Moon Jae-in had called an emergency meeting with his top advisers.

"He said it was an extremely regrettable situation," Novak said. "There were around 100 people in the hospital itself at the time, and another 96 people in an adjacent building, which is akin to a hospice."

Those 96 patients are believed to be safe, she said.

"Questions will be asked about the safety at that hospital the cause of this fire," said Novak.

She added that a month ago, at least 29 people were killed at a sports centre in the south of the country.