A third student has died following yesterday's shooting at a school in Ohio.

A student wounded in a deadly US school shooting was today declared brain dead, authorities said, a day after one student was killed and three others injured when teenager opened fire in the cafeteria at a suburban Cleveland high school.

A teenager opened fire in the cafeteria of a US high school, killing one student and injuring four others before he was chased from the building by a teacher, authorities said.