TWO soldiers have died and a third is in a serious condition in hospital after falling ill during exercises in a mountainous region used to test the fitness of elite SAS troops.

The personnel were said to have been on a routine exercise in the rugged Brecon Beacons in south Wales in temperatures of 29.2C when the tragedy happened on Saturday. The area lies about 40 miles from the elite regiment's headquarters in Hereford. The names of the soldiers and their regiments have not been made public.

David Davies, the Conservative MP for nearby Monmouth said: "It's a terrible tragedy, and I'm sure the Army will hold a full investigation and be doing absolutely everything to find out what went wrong, and prevent that from happening again."

The Brecon Beacons is one of several locations British military use as part of their training. Its rugged and sprawling terrain helps prepare soldiers physically and mentally for warfare, as well as putting their logistic skills to the test – making it an ideal area for elite forces personnel like the SAS.

An MoD spokesman said: "The MoD can confirm that it is working with Dyfed Powys Police to investigate an incident during a training exercise on the Brecon Beacons on Saturday in which two members of military personnel died.

"The two servicemen's next of kin have been informed.

"More information will be released in due course but it would be inappropriate to comment further at this stage.

"Any further enquiries should be referred to Dyfed Powys Police."

The Beacons' jagged topography can prove dangerous even to the most hardened and physically fit. Earlier this year an army captain was found dead on the snow-covered Corn Du mountain. It was thought that Rob Carnegie had been taking part in a gruelling march of 17-40 miles in freezing conditions in the Brecon Beacons as part of a selection process for the special forces regiment, when he collapsed and died.

A spokesman for Dyfed Powys Police said: "A Ministry of Defence exercise was taking place in the area, and they are fully co-operating with our inquiries.

"The next of kin are being informed, and HM coroner has been informed."

The Welsh Ambulance Service also said it had been involved in the incident.

News of the deaths has been met with shock in the nearby town of Brecon, which is home to the Infantry Battle School.

Brecon mayor and Powys county councillor Matthew Dorrance said: "It's incredibly sad for the friends and family of the people who have lost their lives and our thoughts are with the person who is injured."