The Spanish army had on December 21 that two soldiers had died "during manoeuvres" at the Cerro Muriano base near the southern city of Cordoba, without giving details of the circumstances.

But Spanish media reports said the men, aged 24 and 34, had drowned after dozens of soldiers were made to cross a lake in frigid temperatures while carrying their material.

One of the soldiers who drowned, Carlos Leon Rico, had been made to carry an extra 3.5 kilos (7.7 pounds) by his superiors as a punishment, for a total of 12 kilos, his family's lawyer Luis Romero told AFP.

It was not immediately clear if the second soldier who died was also carrying extra weight.

There were no rescue rafts or lifeline at the site of the exercise as should have been the case, Romero said, just a loose rope to guide the soldier.

The "tragedy could have been even worse" since around 60 soldiers were waiting on the bank of the lake to cross, he added.

The Cordoba court that was investigating the deaths handed over the case Tuesday to a military court in Seville at the request of military officials.

Leon Rico's family has appealed the decision, fearing a military court will try to stifle the investigation.

Defence Minister Margarita Robles has said the army will "cooperate without reservations" with the investigation.

"If mistakes were made, they have to be known," she added earlier this month.