Up to 20 people have died and many more were injured when a large tree fell as the result of a storm at the Kintampo Waterfalls in Ghana, emergency officials said.

The tree was brought down by a freak storm and fell into the waterfall, where many students from Wenchi Senior High School were swimming.

Prince Billy Anaglate, a Ghana National Fire Service spokesman, told AFP that 18 students had died at the scene, while two others died in the hospital.

He added that 11 people were receiving treatment, including one of the school administrators who was in charge of the trip.

"We extend our condolences to the families of the dead and pray for the injured," Ghana's tourism minister Catherine Abelema Afeku said in a statement.

The waterfalls at Kintampo are a popular tourist destination in central Ghana.