At least 28 people, including 22 children, have been killed after a Belgian coach crashed in a tunnel in the canton of Valais, Switzerland.

Another 24 children were injured in the crash near Sierre, close to the border with Italy. The children were travelling from Val d’Anniviers and were returning to   Belgium.

The coach, carrying 52 people back to Belgium, hit a wall in the tunnel head-on. Both of the coach’s drivers were among those killed.

The children, from the Belgian villages of Lommel and Heverlee, were returning home after a skiing holiday.

Belgium’s Prime Minister Elio Di Rupo, who is travelling to the scene of the crash, said: “This is a tragic day for all of Belgium.”

The bus crashed shortly after 9:00 p.m. on Tuesday.

At least 28 people, including 22 children, have been killed after a Belgian coach crashed in a tunnel in the canton of Valais, Switzerland

In Brussels, the Belgian foreign ministry said most of the children were aged around 12, and the bus was one of three hired by a Christian group, AFP news agency reports.

The two classes of schoolchildren, from two schools in the Flemish-speaking part of Belgium, had spent a week skiing in Val d’Anniviers, in the Swiss Alps.

Some of the injured were flown by helicopters to hospitals in Lausanne, Bern and other Swiss cities.

Swiss prosecutor Olivier Elsig told a news conference the bus was new, or nearly new, and was equipped with safety belts.

In a tunnel where the speed limit is 100km/h (62 mph), Olivier Elsig said the bus collided with the right-hand side and then hit a concrete wall head-on. An investigation is under way.

Swiss journalist Ruth Seeholzer said some 300 rescuers were working at the scene of the crash.

She said that the two-lane tunnel was not busy with traffic when the accident happened and driving conditions were normal.

Belgian Foreign Minister Didier Reynders said: “It is incomprehensible. There were three buses and only one was in an accident, without any contact with another vehicle.”

The coach, carrying 52 people back to Belgium, hit a wall in the tunnel head-on

A helpline for families has been set up, and many relatives are expected to arrive in Switzerland later.

Belgium has made two aircraft available to take them to Switzerland.

Belgium’s ambassador to Switzerland, Jan Luykx, has travelled to the crash site.

Jan Luykx said: “This tragedy will hit the whole of Belgium. The magnitude of the accident is difficult to take in. For the moment I am concentrating on the practical aspects. The emotional side will come when we meet the families.”

The head of the Valais region, Jacques Melly, expressed his deep sadness at the accident, sending his condolences to the families of the victims and praising the rescuers for their work in “extremely difficult conditions”.