MANCHESTER, United Kingdom - Messages of support poured in for Alex Ferguson after the legendary former Manchester United manager was left fighting for his life following emergency surgery to treat a brain haemorrhage on Saturday.

News of his operation was made public by United, with a statement cautiously optimistic about the prospects for the 76-year-old, the most successful manager in British soccer history.

"Sir Alex Ferguson has undergone emergency surgery today for a brain haemorrhage," the statement said.

"The procedure has gone very well but he needs a period of intensive care to optimize his recovery. His family request privacy in this matter."

According to the Daily Mail, an ambulance was called to the Scot's home in Cheadle, near Manchester, on Saturday morning.

Concerns for Ferguson's health started to mount when it was announced his son, Darren, the manager of English third-tier club Doncaster Rovers, would miss his side's League One match against Wigan Athletic on Saturday because of "family reasons".

"It is tragic. I am going to find out how he is as soon as I possibly can," said Everton manager Sam Allardyce, a long-standing friend of Ferguson's, after the Toffees' 1-1 Premier League draw at home to Southampton.

"Obviously I knew it was extremely serious when I knew his son Darren didn't attend his own game at Doncaster today," the former England boss added. "I hope he has a full recovery."

Southampton manager Mark Hughes, who played under Ferguson during the early days of the Scot's Old Trafford reign, said: "I only just got a little whisper earlier on. I was hoping it wasn't true. I wish him all the best."

'Keep fighting, Boss'

David Beckham, perhaps the most high-profile player Ferguson managed at United, was among several past and present players to offer their support to the "Boss" on social media.

Accompanied by a picture of him as a youngster alongside Ferguson, Beckham wrote on Instagram: "Keep fighting Boss.. Sending prayers and love to Cathy and the whole family x @manchesterunited."

Former United striker Wayne Rooney said on Twitter: "Get well soon Boss. Thoughts with all the family at this sad time. #AlexFerguson."

There was a a particularly heartfelt message from Edwin van der Sar and his wife, Annemarie.

Van der Sar was United's goalkeeper when Annemarie suffered a brain haemorrhage in 2009 from which she has since recovered.

"Devastated about the news about Sir Alex and knowing all too well about the situation ourselves. Stay strong and hope together with everyone you recover. Edwin & Annemarie," the couple's Twitter post read.

Michael Carrick, a current but soon-to-retire United midfielder, said he was "absolutely devastated".

He added: "All my thoughts and prayers are with him and his family. Be strong Boss."

The sympathy extended beyond those with United connections, with Manchester City company Vincent Kompany summing up the mood of messages from rival clubs when he said: "Hang in there Sir Alex. Thoughts are with the family and close ones."

Away from soccer, Scotland's First Minister Nicola Sturgeon tweeted: "My thoughts are with Alex Ferguson and his family - wishing him a full and speedy recovery."

Ferguson retired five years ago when he stepped down as United manager, having won a staggering 38 major trophies, including 13 Premier League titles and two Champions League triumphs, during a 26-year tenure.

He was back at Old Trafford just over a week ago to present a commemorative vase to old rival Arsene Wenger, who will step down as Arsenal manager at the end of the season.

Ferguson had planned to retire at the end of the 2001/02 campaign but changed his mind after speaking to his wife Cathy and their family.

But the death of his wife's twin sister in 2012 provided Ferguson with what he later wrote was a "watershed moment".

"I felt that, after all those years during which Cathy had put me first, it was time that I took care of her needs," he explained.

Glorious reign

Prior to arriving at United, Ferguson, enjoyed considerable success as manager of Aberdeen, helping interrupt Glasgow giants Celtic and Rangers' Old Firm dominance of the Scottish game.

Ferguson, a former Rangers striker, won three Scottish championships, four Scottish Cups and the 1983 European Cup Winners' Cup in charge of the Dons.

He replaced Ron Atkinson as manager of United in 1986 and struggled to revive the club's fortunes initially.

However, the 1990 FA Cup final victory over Crystal Palace gave Ferguson his first United silverware and the Premier League trophy followed in 1992 to kickstart a glorious era for United, the highlight of which was the 1999 treble of Premier League, Champions League and FA Cup titles.

Agence France - presse