Lionel Messi made brilliance look routine with a stunning double to help Barcelona to a 5-0 win over Real Sociedad that restored the champions' two-point lead over Real Madrid at the top of La Liga on Sunday.

Real had gone a point clear thanks to a 3-1 success at bottom side Real Zaragoza, Cristiano Ronaldo blasting in a free kick between goals from Mesut Ozil and Angel Di Maria.

Barca responded in style with another crushing win, a ninth straight league victory for Pep Guardiola's side that took their goal tally to 26 in their last six matches in all competitions.

Messi's brace lifted him to 17 for the season after 15 games, level with Real's Ronaldo.

Barca have 40 points to Real's 38 and the La Liga giants pulled further away at the top of the standings after Villarreal and Espanyol both lost.

Villarreal went down 1-0 at Getafe on Saturday and are eight behind Real, while Espanyol, who squandered the lead to lose 2-1 at Athletic Bilbao on Sunday, are two further back in fourth.

Barca were already two goals to the good at the Nou Camp when Messi bagged his first of the night in the 47th minute after a move of breathtaking skill.

He exchanged close passes six times with Brazil full back Daniel Alves as they sliced through the Sociedad defence for the Argentine World Player of the Year to finish cooly past goalkeeper Claudio Bravo.

His pace and trickery were too much for the visitors and he left at least four Sociedad players for dead when he waltzed across the penalty area and clipped the ball into the net for his second and Barca's fourth in the 87th minute.

David Villa had put them ahead in the ninth minute when Messi sent Pedro clear and the Spain striker diverted his international team mate's cross high into the net.

Pedro chalked up another assist for Barca's second in the 33rd minute when he played a one-two with Andres Iniesta and the Ballon d'Or nominee beat Bravo at his near post.

Substitute Bojan Krkic completed the rout in added time when he finished at the second attempt.

"We have returned to playing at a fantastic level," Messi said in an interview with Spanish television.

"We have worked hard and have a very good team with great players," he added.

Portuguese forward Ronaldo had earlier scored a trademark dipping freekick as Real appeared to have shrugged off any psychological effects from their 5-0 drubbing at Barca at the end of last month.

Ozil opened the scoring in the 15th minute at Zaragoza's Romareda stadium, Ronaldo added the second just before halftime and Di Maria made it three shortly after the break.

Gabi Fernandez pulled a goal back for the home side from the penalty spot in the 54th minute.

"It's one of the best goals I have scored," Ronaldo told reporters.

"I am happy and we want to continue this run," he added.

In the earlier kickoff, David Lopez's stunning freekick and a powerful Fernando Llorente header fired Bilbao to victory at home to Espanyol.

Burly Spain striker Llorente struck in the 73rd minute at the San Mames, his 10th of the campaign, after Pablo Osvaldo had put the visitors ahead in the first half.

Five minutes after his equaliser, Llorente won a freekick around 30 metres out and Lopez stepped up to send a superb drive past goalkeeper Carlos Kameni into the top left corner.

Defeat for Espanyol, who have won all seven of their home games but have a much less impressive away record, means they missed the chance to climb above Villarreal.

The Barcelona-based club have 28 points, four ahead of fifth-placed Valencia, who host Osasuna on Monday.