Barcelona maintained their perfect start to the La Liga season Sunday as Lamine Yamal scored twice in a dazzling display during a 5-0 demolition of Valencia at Mestalla.

The defending champions won their fourth straight league game to move two points clear at the top after Jose Mourinho's Real Madrid suffered a 1-0 defeat at Real Betis on Friday.

Unbeaten Alaves moved into second place with a 5-2 victory over Osasuna, while Valencia remained winless and bottom of the standings after four games.

Fermin Lopez, Raphinha and Pedri also scored for Hansi Flick's Barcelona, who controlled the game from the opening minutes despite playing in a hostile atmosphere at Mestalla.

The result added to the pressure on Valencia's ownership, with thousands of frustrated supporters protesting against the club's leadership and players before and during the match.