Spain's Supreme Court on Friday found five men guilty of raping an 18-year-old at Pamplona's bull-running festival, overturning a lesser conviction of sexual abuse that had sparked large-scale protests by women's groups across the country.

The country's top judges handed down prison sentences of 15 years for the men known as the "Wolfpack" in reference to the name they gave the WhatsApp group in which they shared videos of the 2016 gang rape.

The tougher penalty, upped from the previous sentences of nine years, was imposed following a closely watched hearing that was broadcast live on national television.

The notorious case shook Spain, prompting debate about the nature of consent and moves to reform the law which stipulates the use of physical intimidation or violence for a rape conviction. The admittance, during the original trial, of a defence detective's report on the woman's behaviour after the incident was also widely criticised.

Lawyers for the men had called for their complete acquittal, arguing they could not have realised she did not consent due to a lack of protest or resistance.

Judges in Pamplona acquitted them of rape on that basis in April 2018, a verdict that was confirmed in another ruling in 2018, angering the woman's supporters.