Police in Spain are investigating after an 11-year-old girl gave birth to a baby boy that may have been fathered by her 14-year-old brother.

The child gave birth at Virgen de la Arrixaca hospital in the city of Murcia in southeastern Spain on Friday (2 February).

Investigators believe that the boy is the father and it was reported that he may have been 13 at the time of conception.

It was reported that the girl was admitted with the parents believing that she had "stomach pains" before the baby was born.

But on arrival doctors noticed that she was in the later stages of pregnancy.

Spanish news agency Efe reported that both the girl and her son are doing fine, although both have been taken into the care of the Spanish Ministry of Family and Equality.

Authorities are still waiting for confirmation that the brother is the father of his sister's child, and will investigate if the sex was consensual.

The siblings are believed to have parents that have immigrated from Bolivia and the son may not face any criminal proceedings under Spanish law as he is below the age of criminal responsibility.

The Local, Spain reported that the girl and her parents claim they were not aware of the pregnancy and they believed she had a serious intestinal problem.

Regional Health authority boss Manuel Villegas described the case as "absolutely exceptional" reported The Metro.

"We have to wait now. An investigation is still ongoing and when everything has been clarified, we'll see what has happened and if we can help in some way," Villegas said.

The nation raised the age of consent from 13 to 16 five years ago but an exception exists if intercourse is consensual and when the pair are of a similar age or stage of development and maturity, it was reported.