Roy Keane has announced he is to stop playing football having been advised to do so by both his surgeon and the Celtic club doctor.

A persistent hip injury had raised doubts as to whether the 34-year-old would continue with Celtic, while there were also suggestions that the commute to Glasgow from his Cheshire home was also taking its toll on a devoted family man.

Keane confirmed the news in a statement, stressing it was a decision made on medical grounds.

"Having received medical advice from my surgeon and the Celtic FC doctor, I feel my only option is to retire," he said. "I would like to send the manager, the staff, players and supporters my very best wishes for the future."

The Taoiseach wished Keane well in his retirement and expressed his admiration and appreciation for his "very special contribution to Irish football."

"Over the past decade, he has been arguably the greatest midfield player in world football," Mr Ahern said.

". . .he has established a reputation as one of the true legends of world football. . . and his immense footballing genius is unlikely to ever be forgotten."

Celtic manager Gordon Strachan described Keane as one of the greatest ever players and said it had been a "privilege" to work with the former Ireland captain.

"Roy Keane is one of the greatest ever players to grace the game of football. It was fantastic that we were able to bring him to Celtic and it has been a privilege to work with him.
 
"Even in his short time with the Club, Roy made a great contribution and played an important part in bringing success to the club last season.
 
"We were delighted to make Roy's dream come true when we signed him for Celtic and we were happy when he made our dream come true, by helping us to win the title," added the former Manchester United and Scotland midfielder.
 
"While we would have very much liked Roy to continue for the remainder of his contract, everyone at the club fully understands and respects the decision which he has made.
 
"Roy's retirement will be a loss to Celtic and, of course, a loss to football in general. We would all like to wish Roy and his family all the best for the future. Roy will always be welcome at Celtic Park.
 
Celtic Chief Executive Peter Lawwell added: "Clearly, everyone hoped that we could have enjoyed watching Roy at Celtic for one more season. However, given the medical advice which he has received, Roy feels this is the only option available to him.
 
" While we are disappointed, it is important that Roy's health comes first and we fully respect the decision which he has made.
 
Keane joined Celtic at the beginning of last season after spending 12 years at Manchester United where he won one European Cup, seven league titles and four FA Cups.

He played a pivotal part in United's success after joining from Nottingham Forest for £3.75 million, then a British transfer record, in 1993.

He was the enforcer in a side containing the attacking talents of David Beckham, Paul Scholes and Ryan Giggs but missed what would have been the crowning moment of his career, the 1999 Champions League final victory over Bayern Munich.

Keane was suspended after earning a yellow card in the thrilling semi-final victory over Juventus in which he scored a crucial header to drag United back into the tie.

Renowned for his indomitable will to win and rugged tackling, Keane was United team captain until last his departure following a disagreement with manager Alex Ferguson.

Ferguson has said Keane was the best United player in his 20 years in charge at Old Trafford and "the best midfield player in the world of his generation".

Last month Keane returned to Old Trafford for a testimonial between Celtic and United, watched by almost 70,000 fans.

Keane was Ferguson's on-pitch alter ego - ruthless and uncompromising.

There were occasional bust-ups between the two before Keane left United in November after Ferguson pulled a television interview in which his captain, then injured, made disparaging comments about his team mates.

However, Ferguson is in no doubt about the impact Keane had on United.

"Do you say he was a better player than Cantona, Scholes or Giggs? Of course he wasn't as talented as those players, nowhere near it," Ferguson said last month before the testimonial.

"But without question his obsession with winning, the demands he put on other players and his desire to win football matches made him the most influential player in the dressing room."

After a slow start he helped Celtic to a record points tally and another league title as well as 13th League Cup.

The Corkman never failed to court controversy and was famously sent home from the 2002 World Cup in Japan and South Korea thanks to a very public fallout with then manager Mick McCarthy after he criticised preparations for the Republic of Ireland's campaign.

He came in for fierce criticism and the threat of legal action after admitting in his autobiography that he deliberately tried to injure Manchester City midfielder Alfe Inge Haaland in brutal fashion during a heated Premiership derby with United.

Keane has not yet made it clear whether he will ever pursue a career in football management, but his immediate plans appear to involve spending time with his wife and five children.