A national day of mourning has been declared in Belgium following a coach crash in Switzerland that killed 28 people, including 22 children.
The bus was transporting a school party home to Belgium from a ski trip when it crashed late last night in the canton of Valais, which borders Italy.
Belgian Prime Minister Elio Di Rupo described it as "a black day for our country, all Belgians share our immense sadness, there is no word to express what we feel".
Mr Di Rupo later arrived at Geneva airport and was taken by helicopter to the site of the crash.
At a press conference in the city of Sion, close to the accident scene, Mr Di Rupo said his "first thoughts are with the victims, families and their loved ones.
"We are here ... to try to understand because in our country there is consternation."
Parents of the dead and injured children were flown to Switzerland aboard a government plane.
Some of the parents, gathering at the primary schools in Belgium before boarding a military aircraft, did not know whether their children were dead or alive.
"There's no news, simply no news," said one red-eyed father.
The children on board the bus were mostly school children aged about 12 from Lommel and Heverlee in Flanders.
Deputy Premier and Health Minister Laurette Onkelinx said many of the children injured were in serious condition, including three who were in a coma.
Cause of the bus accident is unknown
The cause of the accident is not yet known, police said.
Police said the bus had just joined the highway towards the Swiss town of Sierre after coming down from the resort.
After travelling 2km on the road, the bus bumped into the curb and skidded into an emergency siding in the tunnel.
The front third of the bus was completely torn apart. Many children were trapped in the wreck and had to be freed, said police.
A Swiss prosecutor has said the coach was not believed to have been speeding at the time.
"The speed of vehicle is being determined. We think the vehicle was not driving too fast," Olivier Elsig told a press conference in the city of Sion.
He said the Swiss authorities were investigating three possible causes: a technical problem, human error or the possibility that the driver suffered a health problem.
Some 200 rescuers worked through the night at the crash scene, while 12 ambulances and eight helicopters ferried the injured to hospital.
Swiss parliamentarians stood for a minute's silence and President Eveline Widmer-Schlumpf said Switzerland would do all it could to support the injured and their families as well as the relatives of the dead.
The bus was owned by Belgian company Toptours, which has a solid reputation, according to Belgian Transport Minister Melchior Wathelet.
He said the driver had arrived at the resort a day before the trip, according to the rules, and that the bus had passed a mechanic's test five months earlier.
Taoiseach Enda Kenny has written to Mr Di Rupo to express his condolences on the loss of life in the crash.
