Lionel Messi scored a penalty and Ansu Fati notched a quickfire brace as Ronald Koeman's Barcelona opened their LaLiga campaign by thumping Villarreal 4-0 at the Nou Camp.

Messi – making his first competitive appearance since informing Barca in August that he wanted to leave, then subsequently deciding to remain for this season – converted a penalty in the 35th minute to put the hosts 3-0 up.

The spot-kick was awarded following a Mario Gaspar foul on teenager Fati, whose superb start to the contest had already seen him score two goals in quick succession.

The 17-year-old Spain international fired in the opener in the 15th minute having received the ball from Jordi Alba's cut-back.

Four minutes later Philippe Coutinho, back from his loan spell at Bayern Munich, drove forward from his own half and fed Fati, who slotted past Sergio Asenjo.

After the subsequent penalty, things got better still for new Barca boss Koeman just before the interval as a Messi delivery was diverted by Villarreal's Pau Torres into his own net.

A considerably less eventful second half saw Messi have an effort pushed over the bar by Asenjo in the 65th minute, send a header wide from an Alba cross, and then thwarted by the goalkeeper again as full-time approached.

Fati was substituted for Ousmane Dembele in the 70th minute to conclude his eye-catching display, delivered just a few days on from the departure to Atletico Madrid of Luis Suarez, who Messi said had been "kicked out".

While Barca claimed maximum points from their opening match, Unai Emery's Villarreal now have four points from three games.

Champions Real Madrid, who won 3-2 at Real Betis on Saturday, have four from two.