A bus caught fire and exploded in northern Colombia yesterday, killing 31 children.

Another 25 people, including one adult, were injured and seriously burned in the blaze.

It happened in the town of Fundacion, in the department of Magdalena.

"The injured have second and third-degree burns, and many are still in a critical condition," said Cesar Uruena of the Colombian Red Cross.

The children aboard the bus were between the ages of one and eight and were returning home after a religious service, Fundacion Mayor Luz Stella Duran told reporters.

Magdalena police said the bus exploded at midday and that the fire was so intense they had problems determining the number of casualties.

The mayor said survivors said the bus driver had been handling a container with petrol aboard the vehicle. Police initially blamed the fire on a mechanical problem.

The driver has vanished, and angry locals went to his home and threw rocks at his windows, the mayor said.

Colombian President Juan Manuel Santos travelled to Fundacion after a final re-election campaign rally in Bogota ahead of the 25 May presidential vote.

"The entire country is in mourning for the death of these children," Mr Santos said upon arriving in Fundacion.

Mr Santos said the government would pay for all hospital and funeral expenses relating to the accident.

The bus, which was being used by an evangelical church group, caught fire close to the church where the children had earlier attended services.