Liverpool's Luis Díaz scored a hat trick as they maintained their perfect Champions League campaign with a barnstorming second-half display in a 4-0 victory over Xabi Alonso's Bayer Leverkusen at Anfield on Tuesday.

Arne Slot's men, who top the Premier League table, provisionally lead the standings of Europe's elite club competition with their fourth win in four matches, with Aston Villa, the only other team with a 100% record, playing Club Brugge in their fourth game on Wednesday.

Leverkusen's loss spoiled the return of manager and former Liverpool hero Alonso, who hoisted the Champions League trophy with the Reds in 2005 and was heavily touted as a replacement for former manager Jürgen Klopp before ruling himself out of the running.

"It's painful the result more than the performance, probably," Alonso told Amazon Prime. "But this is the Champions League, this is the highest level, and today it wasn't enough for us.

"I tried to separate the game and the pain from the result from the nice feelings to come back. I'm really happy and thankful for that reception," he added on the warm greeting he received from the Anfield crowd.

Slot, however, has proved a worthy replacement for Klopp, recording his 14th win in 16 games on Tuesday.

Diaz broke the deadlock of what had been a sluggish affair in stunning fashion in the 61st minute, timing his run onto Curtis Jones' pinpoint pass through the heart of Leverkusen's defence before lifting the ball over keeper Lukas Hradecky.

Gakpo doubled the Reds' lead two minutes later when he dived to head Mohamed Salah's cross home at the back post. The goal was initially ruled offside but the decision was overturned by VAR.

Diaz netted his second in the 83rd minute when he latched onto a cross from Salah, and then held off a challenge before slotting past Hradecky.

"We have top quality players all over the pitch, but actually, I really enjoyed playing in that position today, and wherever I'm playing on the pitch, I'm going to work hard, and I hope I can help the team," Diaz said, adding he planned to go and search for the match ball.

He completed his hat trick with a tap-in from close range in stoppage time after Darwin Núñez's shot was blocked in a statement victory for the six-times winners of Europe's top competition against the Bundesliga champions who lost just once in all competitions last season.

"Four-nil, good result against a very good team, I don't know if it's the best result [this season], but it's a good one," Gakpo told Amazon Prime.

Both teams were lacking quality in the final third in a dull first half. Leverkusen's Jeremie Frimpong had an effort shortly before half-time chalked off for a handball in the build-up, while Gakpo squandered a terrific chance for Liverpool, shooting straight at Hradecky after working the ball up the left side.

Alonso's Leverkusen are provisionally 11th in the Champions League standings with a pair of wins, a draw and a loss.

The 42-year-old Alonso played 210 games for Liverpool in a five-year spell from 2004, and was part of the side that completed a miraculous comeback in their Champions League final win over AC Milan in Istanbul.