SEOUL - A fire at a hotel in South Korea has killed seven people and injured 12 others, fire authorities said on Friday.

The fire began on the eighth floor of the nine-story hotel in Bucheon, just west of the capital Seoul at around 7:40 pm (1040 GMT) on Thursday, before being put out in about two hours, according to the interior ministry.

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Seven people died, mostly guests, and 12 were sent to hospitals for treatment, including three in critical condition, said Lee Sang-don, an official at the Bucheon fire station.

Among those killed were a couple who jumped out the windows onto an air mattress installed in front of the building, Lee said.

"It was unfolded normally but appeared to have flipped over when they jumped down," he told a televised briefing.

Authorities were looking into the exact cause of the incident, adding there were no sprinklers inside, which was not mandatory when the building was completed in 2003, Lee added.

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Interior Minister Lee Sang-min ordered all-out rescue efforts by mobilizing all available resources, the ministry said.

Some 70 vehicles and 160 firefighters were dispatched to the scene, Yonhap news agency said, citing provincial fire authorities.