Aritz Elustondo's early red card gave Hansi Flick's side a comfortable afternoon with Gerard Martin, Marc Casado, Ronald Araujo and Robert Lewandowski on the scoresheet.

Atletico Madrid beat Athletic Bilbao on Saturday to temporarily knock the Catalans from their perch, while Real Madrid, third, lost at Real Betis.

Flick was able to rotate his side a little ahead of the Champions League last 16 visit to face Benfica on Wednesday.

Real Sociedad, ninth, threatened in the opening stages but fell foul of Barcelona's offside trap, with Sergio Gomez's strike ruled out.

At the other end Barcelona playmaker Pedri Gonzalez came close when he pressed La Real goalkeeper Alex Remiro and deflected his attempted clearance just over and onto the roof of the net.

The game swung Barcelona's way when Elustondo was sent off in the 17th minute for pulling down Dani Olmo as he ran in behind him through on goal.

The hosts took the lead after 25 minutes when Olmo chipped the ball across for Martin to fire home the first goal of his career.

Four minutes later Barca had their second, with Olmo involved again, this time his wayward shot deflected home by team-mate Casado.

The enterprising Lamine Yamal teed up Pedri but Remiro saved his shot from the edge of the box as Barca dominated.

Pedri came close again after the break with an effort from range which bounced back off the crossbar, shortly before Araujo nabbed the third.

Remiro pushed out Lewandowski's header from corner but Araujo was on hand to nod home the rebound.

Lewandowski cleverly converted Barcelona's fourth when Araujo's low drive from distance prodded home by the veteran Polish forward.

The 36-year-old leads the league with 21 goals in 25 appearances.

Barcelona played out the final half hour without incident, occasionally threatening, with substitute Ferran Torres twice coming close to a fifth.