Former Prime Minister Jose Luis Rodríguez Zapatero, under investigation for corruption, said Thursday that luxury jewellery found by investigators during a search of his office was a gift from a foreign country.

Zapatero, who governed Spain from 2004 to 2011, was placed under formal investigation in May for alleged influence peddling in connection with the bailout of small airline Plus Ultra in 2021.

A police search of Zapatero's office found jewellery and luxury watches valued at €1.3 million ($1.5 million), leading the investigating magistrate in charge of the case to probe additional alleged offences of tax fraud and smuggling.

During his first interview since he was put under investigation, the former Socialist leader told Spanish public television the jewellery and luxury watches had been received "many years ago" as "a courtesy gift".

"I am not going to name the country because the justice system should be the first to know," Zapatero said, adding that he "probably should have" refused the gift.