Liverpool's hopes of winning the Europa League were left hanging by a thread after they lost 3-0 at home to Atalanta in the first leg of their quarter-final tie on Thursday, while Bayer Leverkusen beat West Ham United to extend their unbeaten record this season.

Liverpool are hoping to make this season's Europa League final in Dublin on May 22 their final game before Jurgen Klopp steps down as manager, but they face a monumental task to turn their last-eight tie around after a stunning Atalanta performance.

Liverpool, who started with Mohamed Salah and Dominik Szoboszlai among the substitutes, saw Harvey Elliott come agonisingly close to opening the scoring with a shot that hit the bar and struck the post on its way back out.

Atalanta then took the lead seven minutes before half-time when Davide Zappacosta's low ball in from the right was finished off first-time by former West Ham striker Gianluca Scamacca.

The same player made it 2-0 on the hour with a fine finish from Charles De Ketelaere's assist.

Salah, who had come on at the start of the second half, then had a goal disallowed for offside before Atalanta made it 3-0 with seven minutes left.

Caoimhin Kelleher spilled a shot by Ederson and Croatian midfielder Mario Pasalic, who once belonged to Chelsea but did not play a first-team game, followed in to score.

The stunning victory for the side who sit sixth in Serie A ends Liverpool's 33-game unbeaten run at home.

"It hurts, we didn't lose here for a long time," said Liverpool captain Virgil van Dijk. "They punished us for being sloppy in possession.

"This will definitely hurt tonight and then from tomorrow we need to switch it back on to get a result."

Recent history suggests there is still hope for Klopp's side, as they won 5-0 away to Atalanta in Bergamo in the Champions League group stage in 2020/21, a campaign in which they also lost to the Italian side at Anfield.

In Germany, Bundesliga champions-elect Leverkusen made it 42 games without losing in any competition this season as they beat West Ham 2-0 to seize control of their quarter-final tie.

Jonas Hofmann and Victor Boniface both came off the bench to score late goals for Xabi Alonso's side, with the opener arriving in the 83rd minute and the second coming in injury time.

The victory continues what could be a stunning week for Leverkusen, who are 16 points clear of Bayern Munich in Germany and can win their first Bundesliga title by beating Werder Bremen at home on Sunday.

Alonso told reporters "the anticipation is huge -- it couldn't be bigger."

"We have a chance on Sunday -- if we win, we're champions. We need to step on the gas and it would be something very special to achieve," he said.

If Leverkusen finish the job against West Ham, they will advance to a semi-final against either AC Milan or Roma, who clashed at San Siro in the first leg of their quarter-final on Thursday.

Roma ran out 1-0 winners on the night away to their Serie A rivals thanks to Gianluca Mancini's 17th-minute header from a corner. Mancini had also scored the winner in the Rome derby against Lazio last weekend.

"It's a great night for us. I couldn't have asked for more from this week," Mancini told broadcaster Rai.

Thursday's other game saw Benfica beat Marseille 2-1 in Lisbon in the first leg of their quarter-final.

Goals by Rafa Silva and Angel Di Maria either side of the break put the Portuguese side firmly in command, but Pierre-Emerick Aubameyang's goal midway through the second half gives Marseille hope for the return next week.

Aubameyang is the Europa League's all-time top scorer and has 10 goals in 10 games in the competition this season.