Barcelona are back in form and La Liga's big three are back at the top of the table after the defending champions put on a finishing masterclass to thrash Sevilla 4-0 on Sunday.

Lionel Messi scored his first goal of the season by curling in a brilliant free-kick at Camp Nou after three goals in eight minutes from Luis Suarez, Arturo Vidal and Ousmane Dembele had already put Sevilla out of sight.

"It was crucial for us," said coach Ernesto Valverde whose team ended the game with nine men.  "It has been a strange start to the season and we have not added all the points we would have wanted."

Suarez launched the flurry, his stunning left-footed bicycle kick arguably even better than the volley he scored in the Champions League win over Inter Milan on Wednesday.

Vidal then finished a superb passing move that involved all 11 Barca players, and Dembele powered through to make it three before Messi added a fourth in the second half.

The match descended into farce late on as Barcelona's debutant Ronald Araujo was sent off and Dembele followed after collecting a second yellow card for dissent.

The referee's report said Dembele was dismissed for calling Mateu Lahoz "very bad". He could now miss the Clasico on October 26.

"Dembele is a mystery," said Valverde.

"It is very difficult to get words out of him in Spanish, so what he said couldn't have been very long." 

By then, the game was long gone as victory pushed Barcelona up to second in the table, two points behind Real Madrid and one above Atletico, who could have done with some of the Catalans' classy finishing in their goalless draw away at Real Valladolid.

For all the turbulence and scrutiny on Valverde and Zinedine Zidane, Barca and Madrid head into the international break not only as the league's two front-runners, but also with confidence and momentum.

Eden Hazard scored his first goal for Madrid in their 4-2 win over Granada on Saturday and Barca's star man is off the mark as well after his own injury-interrupted start to the season.

This was Barcelona's fourth consecutive victory. Messi's return has increased the pressure on Antoine Griezmann, who was left out of the starting line-up following his quiet display against Inter. Dembele was preferred on the left of the front three.

Sevilla, which dropped to sixth, had eight shots to Barcelona's seven in the first half but were three down at the break.

RCD Espanyol's Chinese forward Wu Lei was in the starting line-up and finished the full match against RCD Mallorca, but the team's 2-0 loss made the Catalan club stand at the last second place of the league table.

For other matches on Sunday, RC Celta won 1-0 over Athletic Bilbao, Valladolid made a goalless draw with Atletico de Madrid, and Real Sociedad lost to Getafe 1-2.

(With input from AFP)

(Cover: Luis Suarez scores the first goal with a bicycle kick for Barcelona during La Liga match against Sevilla at Camp Nou in Barcelona, Spain, October 6, 2019. /VCG Photo)