Earlier, Barca's front three of Lionel Messi, Luis Suarez and Neymar all struck in a 6-0 thrashing of Alaves.
Madrid also have two games in hand on their title rivals.
Alaves to face Barcelona in Copa del Rey final
However, both games were overshadowed by horrible injuries as Barca's Aleix Vidal suffered a dislocated right ankle that will keep him out for five months and Osasuna's Tano Bonnin a double leg fracture.
"There is no such a difference [between the sides]. It is true it was the leader against last in the table, but you have to play the games and the opponents always make it difficult against Madrid," said Real boss Zinedine Zidane. "We have to suffer, but in the end we got what we came for."
Real extend La Liga lead with 3-0 win over Sociedad
Barca's success was also soured by violent clashes between fans outside the ground before kick-off which left one supporter in hospital with serious head injuries.
Both sides later released statements condemning the violence.
"I go away with very good feelings from the football perspective, for the result and the way we achieved it," said Barca boss Luis Enrique. "But I am upset by Aleix's injury, the way it came about and what it means for him."
Barcelona, Sevilla maintain pressure on Real Madrid
Barca confirmed Vidal underwent surgery on Saturday night that will keep him out for the rest of the season.
Elsewhere, Athletic Bilbao moved up to seventh with a 2-1 win over Deportivo la Coruna, whilst Betis and Valencia played out a 0-0 draw.
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