Celtic chief executive Michael Nicholson has backed manager Martin O’Neill despite a "painful" week.

The Parkhead club lost twice to Rangers - in the League Cup quarter-finals and Scottish Premiership - plus at home to Ferencvaros in their Europa League opener. It follows last month's collapse against LASK in their Champions League play-off, losing the tie on aggregate despite leading 4-0 at one stage.

Following the second Old Firm defeat, O'Neill said he was going to reflect on his future and admitted "it might be time to wrap it up". While Nicholson admitted "the losses in the last week have been painful for us all", he insists the club "will now come together and support Martin and the players, as we focus our efforts on achieving success domestically and in the Europa League."

O'Neill's return to Celtic last October - 20 years after his first spell as manager - came following the resignation of Brendan Rodgers. Another spell as interim boss followed weeks later as Wilfried Nancy was sacked after a dismal 33-day tenure. Nicholson added that the club "owe a debt of gratitude" to O'Neill and his management team for stepping in twice last season, and says the club were "delighted" he agreed to return on a permanent basis this summer.