Basque militant Inés del Río has been freed after the Spanish authorities upheld a European Court of Human Rights ruling against her continued detention.

She had been serving a 30-year sentence for bomb attacks in the 1980s.

Monday's ruling by the European Court of Human Rights "gives us no choice", concluded a prosecutors' report at the High Court requesting Del Rio's immediate release, reported El Pais newspaper.

The penal chamber subsequently ordered her immediate release.

Antton Troitiño, another Basque militant, detained in Great Britain, also walked free (on bail) after the English Supreme Court has examined the appeal presented by his lawyers in which they asked the European Court's sentence to be applied to his case as well. 

Parot doctrine

Del Rio was arrested in 1987. She was later sentenced to more than 3,800 years in jail, but the criminal code in force at the time reduced this to a maximum stay of 30 years.

Eta declared an end to its armed campaign in 2011.

Del Rio earned sentence reductions through prison work, making her eligible for release in July 2008 - but two years earlier the High Court applied what is known as the "Parot doctrine" to extend her detention.

Under this doctrine, sentence reductions are applied to the sentences for individual crimes - collectively amounting to 3,828 years - rather than the overall 30-year maximum stay.

It meant Del Rio's release would be postponed until 2017.