Ronny Deila is to quit as Celtic manager at the end of the season, with the Scottish Premiership leaders saying it was the Norwegian's decision, reports BBC Sport.

Neil Lennon, who Deila succeeded in 2014, has already said he would welcome a return to the Scottish champions.

"There have been some disappointments and times when we have not achieved what we had hoped for," he said.

"I'm realistic and honest enough to admit that."

Republic of Ireland assistant manager Roy Keane has been mentioned as a possible replacement, while two other former Celtic players - David Moyes and Malky Mackay - have not distanced themselves from the job in recent weeks.