Andreas Christensen, Robert Lewandowski and Raphinha struck for the hosts at Camp Nou with Guido Rodriguez netting a late own goal to round off the rout.

Edgar Gonzalez's early dismissal made it an easy night for Xavi Hernandez's side, who restored their 11-point lead with six games remaining after second place Real Madrid had thrashed Almeria 4-2 to cut the gap.

With his side comfortably winning, Xavi brought on 15-year-old forward Lamine Yamal to become the club's youngest ever player to debut in La Liga.

Betis also brought on veteran Joaquin Sanchez, 41, for his final appearance at Camp Nou before he retires at the end of the season, and he was afforded a standing ovation by Barcelona supporters.

The Catalans bounced back from a 2-1 defeat by Rayo Vallecano in midweek.

"The last game was very tough for us, we knew that we needed to respond and this game was important," Raphinha told Movistar.

"We know what we can do and what we were missing in the last game. We needed more attitude, to have more of the ball, and to win the league you have to do that in every game."

Xavi brought Christensen into the starting line-up after injury, but French winger Ousmane Dembele had to make do with a place on the bench after his three month lay-off.

The Danish defender, who has been crucial this season after arriving on a free transfer from Chelsea, made a quick impact on his return.

Raphinha whipped in a vicious ball which Ronald Araujo narrowly missed but Christensen followed in behind to power a header home.

Betis were set back further when defender Edgar was dismissed for two bookings after half-an-hour, having only come on in the 13th minute to replace the injured Luiz Felipe.

The second yellow for treading on Pedri's foot seemed a little harsh and Betis protested bitterly, with coach Manuel Pellegrini booked for his complaints.

- Floodgates open -

Lewandowski pounced soon after to net his 19th league goal of the season after Jules Kounde set him up with a low cross.

The Pole, La Liga's top scorer, reacted after Real Madrid's Karim Benzema earlier netted a hat-trick against Almeria to move within one of his tally.

Three minutes later Raphinha struck the third, making a clever run in behind the defence and finishing from Sergio Busquets' chipped pass -- a connection Barcelona have profited from on other occasions this season.

It was Raphinha's 10th goal of the campaign across all competitions, and after a long wait while VAR checked if he was offside, the Brazilian was able to celebrate.

Lewandowski hit the post early in the second half after a fine Pedri through ball as Barcelona looked to continue racking up the scoreline in the pouring rain.

Xavi brought on Dembele with little over 15 minutes to go, with Camp Nou delighted to see the winger back.

There was further applause for Joaquin as he limped off injured, putting his hope of becoming the league's all-time record appearance maker in jeopardy.

Rodriguez deflected in Ansu Fati's cross as Barcelona added a fourth goal in the 82nd minute.

Almost 90,000 home supporters were also treated to 15-year-old Yamal's debut in the final stages, and the winger came close to scoring with a shot repelled by Rui Silva.

"We were talking about this on the bench, when I was at 15 I think I was playing for my neighbourhood team," added Raphinha.

"And seeing him come on in this stadium, with all these people, is incredible."