Felipe Juan Froilán, the 13-year-old son of the infanta Elena and Jaime de Marichalar, is in hospital after shooting himself in the foot on Monday with a 36 calibre shotgun at the family home in Soria.
According to a statement released by the royal household, the king's grandson "has suffered an accident whilst he was practising shooting at the Marichalar family farm in Soria".
The statement goes on to say that the young infante was "on the terrace with his father and a 36 calibre shotgun went off accidentally" causing him "an injury to the right foot".
He was initially treated at a local hospital, but was then transferred to the Hospital Quirón in Madrid, where he remains under observation after having the wound "surgically cleaned".
The incident has caused considerable embarrassment for the royal family as under Spanish law, children under the age of 14 are prohibited from using any guns, even air rifles. Nevertheless, Felipe Juan Froilán, who is only 13, was using a 36 calibre shotgun, usually used for hunting small game.
A police source has confirmed that "the use of any arms without a licence or in contradiction of the established rules" should be subject to a fine of between 300.52 and 601.01 euros and the weapon in question should be confiscated.
The accident is also a painful reminder for the Spanish monarch, who 56 years ago in exile in Estoril in neighbouring Portugal, was involved in a shooting accident in which his younger brother Alfonso, 14, was killed.