Barcelona thrashed Sevilla 4-0 helped by a Lionel Messi double as they took full advantage of Real Madrid's defeat at Bilbao in La Liga on Saturday.
Unbeaten Barca extended their lead to five points with just under half the season played after Real Madrid slumped to a 1-0 defeat at Athletic Bilbao's San Mames following a third-minute Fernando Llorente header.
Barcelona, ousted from the Copa del Rey by Sevilla in midweek, have 46 points from 18 games ahead of Real on 41 with Valencia, who host local rivals Villarreal on Sunday, third on 35.
Barca exerted their usual dominance from the start at a rainy Nou Camp and Zlatan Ibrahimovic, Thierry Henry and Messi all went close before Sevilla defender Julien Escude diverted a Rafael Marquez cross high into his own net in the 49th minute.
A perfectly weighted, defence-splitting pass from midfielder Xavi with 20 minutes left released substitute Pedro who lifted the ball over advancing Sevilla goalkeeper Andres Palop, before Messi finished from close range in the 85th.
The Argentina forward, who grabbed a hat-trick at promoted Tenerife last weekend, then raced on to an Eric Abidal pass in the first minute of added time to score his 14th goal of the campaign, two more than nearest rival David Villa of Valencia.
Earlier in the day Bilbao's inspired goalkeeper Gorka Iraizoz denied Real's expensively-assembled strikeforce and a third loss of the campaign for Manuel Pellegrini's side leaves them on 41 points from 18 matches.
Bilbao stormed out of the blocks at their packed and intimidating San Mames stadium and midfielder Carlos Gurpegi and striker Gaizka Toquero were denied only by the frame of the goal inside the first minute.
Shell-shocked Real were a goal behind two minutes later when Lassana Diarra could only head a Fran Yeste corner into the path of Fernando Llorente and the unmarked striker stooped to nod the ball past keeper Iker Casillas.
Karim Benzema, Cristiano Ronaldo and Kaka all had numerous chances to level but Iraizoz was only beaten once when a Benzema shot bounced back off the inside of the post in the 34th minute. Gurpegi was sent off in the fifth minute of added time when he was shown a second yellow card.
Juanfran and Walter Pandiani struck inside 10 minutes to fire Osasuna to a 2-0 home win over Espanyol in La Liga on Saturday to lift the Pamplona-based club to 12th.
Midfielder Juanfran netted through a crowd of players in the seventh minute. An unmarked Pandiani nodded home two minutes later before Osasuna midfielder Ruper was shown a second yellow card four minutes before the break.
Espanyol were also reduced to 10 men four minutes into the second half at the Reyno de Navarra when defender Facundo Roncaglia picked up a second booking.