Hailed by women's rights groups, the Supreme Court's ruling accepted the victim's ordeal met the requirement in Spanish law that the plaintiff in a rape case must present evidence of intimidation or specific violence.

The woman was 18 when she was gang-raped in a doorway early in the morning at the 2016 San Fermin festival by the five men who called themselves the "Wolf Pack".

Her lawyers argued shock and fear had stopped her from fighting them.

The Supreme Court agreed, saying the attack "cannot be considered a crime of sexual abuse, but a crime of rape ... because the factual account describes a scenario of true intimidation, in which the victim did not at any moment consent to the sexual acts carried out by the accused".

In proceedings broadcast live on national television, the Supreme Court increased the mens' sentence to 15 years in jail rather than the nine years they had been given for sexual abuse by the regional court.

Both the woman and the five men had appealed to Spain's highest court following the original conviction and sentencing.

The men, who included a serving police officer, had shared videos of the incident in a WhatsApp group and joked about it shortly afterwards.

The teenager was found crying on a bench by a couple who rang the police when she said she had been attacked.

One of the men was sentenced to an additional two years in jail for stealing the victim's phone.

They collectively need to give 100,000 euros ($A163,559) as compensation to the victim.

The defendants' lawyers had argued the woman consented to sex.

"The victim could have said 'no'," lawyer Agustin Martinez told the court. The lower court had said the men could not be convicted of rape without proof they had used physical violence.

But Spain's public prosecutor Isabel Rodriguez agreed in court that violence and intimidation were used.

"You can't ask victims to act in a dangerously heroic way," she said.

Australian Associated Press