Photos of the scene in Seongnam, just south of Seoul, showed a deep concrete shaft under the broken grate. Seongnam city spokesman Kim Nam-jun announced the deaths in a televised briefing and said 11 other people were seriously injured.

A man who was involved in planning the concert was found dead early Saturday in an apparent suicide.

Fire officials, speaking on condition of anonymity because of office rules, said the victims were standing on the grate while watching an outdoor performance by girls' band 4Minute, which is popular across Asia.

About 700 people had gathered to watch the concert, which was part of a local festival. Fire officials said many of the dead and injured appeared to be commuters who stopped to watch the concert after leaving work. Most of the dead were men in their 30s and 40s, while five were women in their 20s and 30s, they said.

Kim said it was believed that the grate collapsed under the weight of the people. Prime Minister Chung Hong-won visited an emergency center in Seongnam and urged officials to focus on helping the victims' families and ensure the injured get proper treatment, Kim said.

A video recorded by someone at the concert that was shown on the YTN television network showed the band continuing to dance for a while in front of a crowd that appeared to be unaware of the accident.

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