The Duke and Duchess of Cambridge have offered their condolences to the families of the 74 people who died in a train fire in Pakistan.

In a letter to the country's president Arif Alvi, William and Kate said they were "horrified and deeply saddened" to hear of the incident near the town of Rahim Yar Khan.

Three carriages were consumed as the fire, which was caused by a cooking gas stove, ripped through the train.

Most of those who died were members of Tableeqi-e-Jamaat, an organisation of Islamic missionaries.

It is believed the blaze started in their compartment.

Survivors said it took almost 20 minutes for the train to stop and dozens of panicked people jumped from the train.

These reports came in contrast to that of the train's conductor, Sadiue Ahmed Khan, who said the train's emergency braking system was in perfect working order and the train had stopped within three minutes of the first signs of fire.

An official statement from Kensington Palace said: "Our thoughts and prayers are with all the people and families affected by this heart-breaking disaster. "

William and Kate recently returned from a five-day royal tour of Pakistan to strengthen ties between between London and Islamabad.