Barcelona's fortunes took another downward turn after Benfica beat the beleaguered Catalan club 3-0 in Champions League group stage action on Wednesday.

It was the second straight loss in the competition by a three-goal margin for Ronald Koeman's side, following a loss to Bayern Munich by the same scoreline two weeks ago.

It adds further pressure to Koeman, whose has come under immense criticism and could potentially be sacked amid a equally lacklustre start to the LaLiga season.

"At the end of the day, they easy thing is getting rid of the coach, but we are all responsible. The truth is we're in a critical situation," Barca captain Sergio Busquets said.

"We're only two games into the group stage. We need to focus on improving.

"We need to win our next two games against Dynamo Kiev and see how the other two get on. There's a long way to go and we need to try and be positive."

Uruguay star Darwin Nunez had two goals for Benfica on the night to lead the Portuguese powerhouse to the win at an electric night in Lisbon. Nunez's first goal came just three minutes into the game when he raced past Barca's backline and cut in on the left for the near-post finish.

Benfica's Lucas Verissima then made a last-ditch block to deny Luuk de Jong from close range as Barcelona looked to get back into the game, but they were second best throughout.

Jorge Jesus' side continued to mount pressure after the break, with Rafa Silva doubling Benfica's lead in the 69th minute when he pounced on Joao Mario's initial shot.

Benfica continued the onslaught when Nunez saw a shot clip the wordwork after beating Marc-Andre ter Stegen to a through ball.

But Nunez got his brace when he converted a penalty in the 79th minute after Sergino Dest was booked for a handball inside the box.

Barcelona finished the night with 10 men after Eric Garcia shown his second yellow card on the night.

Barca are bottom of Group E with no points from two games, six behind leaders Bayern and four adrift of Benfica. Dynamo Kiev are third place in one point.