Ten people were killed and 17 others were injured when a pre-dawn fire engulfed a nursing home for senior women Friday in the southeastern port city of Pohang, according to local media.

The fire erupted shortly before 04:30 a.m. local time, scorching the two-story building and prompting 20 fire trucks and 200 firefighters to be dispatched. The fire was put out in about half an hour, but its cause remained unclear, South Korean news agency Yonhap quoted the authorities as saying.

Those killed ranged from 71 to 90 in age. Most of them suffocated as their illnesses made it difficult to quickly evacuate the scene, fire officials said.

The nursing home was privately operated, and all of the deaths occurred on the first floor, the officials said.

Pohang is 374 kilometers south of Seoul. It houses one of the largest steel mills in the country.

President Lee Myung-bak expressed regret over the tragedy, his spokeswoman Kim Hee-jung said.

"President Lee said the deaths of the elderly people by the unfortunate incident are regrettable," she said, adding that the president made the comments while receiving a report on the fire early in the morning before heading to the G-20 summit venue.

Lee instructed Prime Minister Kim Hwang-sik to deal thoroughly with necessary government measures in connection with the incident, the spokeswoman said.