A tourist bus crashed into the wall of a tunnel in the canton of Valais, Switzerland, killing at least 28 people, including 22 children, it has been reported.

The two bus drivers were also killed in the accident and as many as 24 children were injured in the tragedy on Tuesday night.

The bus was carrying 52 passengers from the cities of Lommel in northeast Belgium and Heverlee near Louvare and was returning home after a skiing holiday when the accident happened.

Most of the children were aged around 12 and the bus was one of three hired by a Christian group, the AFP has reported quoting the Belgian foreign ministry.

Rescue workers rushed to the spot and the injured were flown by helicopters to four Valais hospitals, the BBC has reported.

The cause of the accident is not known yet and the Swiss police have started an investigation on the accident.