Another 37 people were injured in the accident, which occurred as the victims were returning from Peruvian capital Lima following Barcelona de Guayaquil's Copa Libertadores qualifying win over Sporting Cristal on Thursday.
Authorities said the crash occurred near the town of Los Organos in Piura province, around 150km south of Peru's border with Ecuador.
"Our deepest solidarity with the families of the deceased Barcelona fans in the accident in Peru," Ecuadorian President Lenin Moreno said in a statement. "We are coordinating assistance to all of those affected."
Alejandro Dominguez, the president of South American football governing body CONMEBOL, also expressed his sorrow in a social media post.
"I deeply regret the death of eight young Barcelona supporters," he said. "I send my condolences to families and close ones at this sad time."
Fatal traffic accidents are frequent in Peru because of dangerous roads. Police said they were investigating Saturday's incident.