GENEVA — A yearlong conflict is threatening to cause a humanitarian catastrophe in Yemen, one of the world’s poorest countries, the United Nations reported on Tuesday, saying that “children are paying the highest price.”

The effects of the conflict and the deteriorating humanitarian conditions have brought Yemen “to the point of collapse,” Unicef, the United Nations Children’s Fund, said in a report, adding that the country was at risk of becoming a failed state.

At least six children have been killed or maimed in the fighting every day for the past year, Unicef said, calling that “the tip of the iceberg” because that number represented only the cases that had been verified. The toll is almost certainly much higher, the organization said.