Arsenal have sacked coach Unai Emery after seven matches without a victory, with Freddie Leungberg temporarily taking over as coach.
Emery leaves the club after 18 months in charge and is eighth in the Premier League after four wins in 13 games.
"The decision was taken because the performance and results are not up to the required level," the club said in an official statement.
"We asked Freddie Leungberg to take charge of the first team on a temporary basis. We have full confidence in Freddy to lead us forward."
Arsenal suffered their last defeat on Thursday with a surprise home defeat at home to Eintracht Frankfurt 2-1 in the fifth round of Group F.
Despite the loss, Arsenal are top of the group with 10 points, one point ahead of Germany, but have yet to qualify for the knockout stages.