Lionel Messi plundered a hat trick and substitute Ousmane Dembele came off the bench to set up a late goal for Luis Suarez as Barcelona romped to a 5-0 win in the Catalan derby against Espanyol at the Camp Nou.
With both title rivals Real Madrid and Atletico having dropped points with draws earlier in the day, Barcelona were looking to strike an early blow at the top of the table.
Messi set Barcelona on their way with the opening goal after 26 minutes, although looked to have been offside.
The Argentinian playmaker then doubled the lead 10 minutes before half-time, and completed his hat trick just after the hour.
Gerard Pique's header made it 4-0 with three minutes left before Dembele, on as a late substitute, laid a fifth on a plate for Suarez in stoppage time.
After a slow opening, Barcelona took the lead after 26 minutes. Ivan Rakitic picked out Messi in the right side of the penalty area, and the Argentina playmaker sidestepped defender David Lopez before lashing the ball into the top corner.
However, replays showed Messi had been at least a yard offside as the Espanyol back line stepped up.
Pau Lopez made a fine save to deny Rakitic after he raced clear before Barcelona did go 2-0 ahead in the 35th minute, with another fortuitous goal.
As Messi looked to dart into the left side of the penalty box, the ball cannoned up off an Espanyol defender, before then being hit against team-mate Pape Diop.
The deflection put the ball into the path of Jordi Alba, who cut a pass back across the six-yard box for Messi to stab past Lopez.
There was, though, a let-off for Barcelona just before half-time when Espanyol forward Pablo Piatti saw his shot crash against the far post.
The visitors missed another great chance to reduce the deficit early in the second half when full-back Alba inadvertently laid the ball off to Piatti as Marc-Andre ter Stegen had come out to collect a long ball up field.
Piatti, though, could only clip an attempted lob past the far post with the goal wide open.
Uruguay forward Suarez, who only returned from international duty on Friday, looked to be having one of those nights as he sent a cut-back from Messi over from six yards.
Samuel Umtiti blocked a goal-bound strike from Espanyol winger Leo Baptistao before Barcelona wrapped things up after 67 minutes.
Messi fed Suarez, who in turn laid the ball out to Alba on the overlap down the left and his cut-back was coolly dispatched into the bottom corner by the Argentinian.
It was his first hat trick in La Liga since March 3, 2016 at Rayo Vallecano. He ended a drought of 554 days without a league hat trick, his second-longest such stretch.
His three league hat tricks against Espanyol are tied for the most against a single opponent with Osasuna and Valencia.
With the result secure, Ernesto Valverde sent on Dembele in the 68th minute to make his debut, replacing Gerard Deulofeu to great applause from the Nou Camp faithful.
The French winger produced a quick show of footwork to turn Aaron Caricol, only to be brought down by the left-back, who was swiftly shown a yellow card.
Ter Stegen produced another fine save to tip away an angled drive by Espanyol substitute Didac Vila, before Pique headed in from a corner with three minutes left.
Suarez added a fifth in the closing moments, after the ball had been played across the penalty area from the right directly into his path by Dembele.
The comprehensive win puts Barcelona, who host Juventus in the Champions League on Tuesday night, two points clear at the top of the table, having yet to concede a goal in their three La Liga victories.