The accident happened early on Wednesday at Menjar Shenkora Arerti Mariam Church in Amhara, northern Ethiopia, as worshippers gathered for an annual event celebrating St Mary.
Many worshippers had climbed up the wooden scaffolding to see a ceiling mural when the support structure collapsed, according to witnesses.
"We all had gathered in prayers when all of a sudden the scaffolding collapsed and people starting falling from the ceiling," witness Mikias Mebratu, who lost three of his friends, said at the scene.
Seyoum Altaye, a clinician with a local hospital, said the victims include some children and elderly people.
"So far we have confirmed 25 dead and over a hundred injured," he said.
He said the hospital is seeking support from the Red Cross to look after the injured.
Teshale Tilahun, the local administrator, warned that the death toll could potentially rise.
"It is a tragic loss for the community," he said.
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