Sir Alex Ferguson remains in a serious condition at the Salford Royal Hospital following a brain haemorrhage as the football world rallies to his support with a deluge of messages wishing him well.

The 76-year-old former Manchester United manager underwent emergency surgery after he was rushed by ambulance from his home in Wilmslow, Cheshire on Saturday.

He was taken first to Macclesfield district hospital and then to Salford hospital under a police escort. His family, including his wife Cathy and his son Darren, also a football manager, were understood to be at his bedside.

Neither the club nor the hospital provided an update on his condition on Sunday which United had previously said would require intensive care. The team issued a statement in a tweet with a picture of Ferguson that read:

Manchester United (@ManUtd) "Please. Be strong. Win this one."

The statement contained messages of support from 17 current and former players including Wayne Rooney and Eric Cantona.

The club Ferguson managed for almost 27 years until retiring in 2013 said on Saturday: “Sir Alex Ferguson has undergone emergency surgery today for a brain haemorrhage. The procedure has gone very well but he needs a period of intensive care to optimise his recovery. His family request privacy in this matter.”

It added: “We will keep Sir Alex and his loved ones in our thoughts during this time, and we are united in our wish to see him make a comfortable, speedy recovery.”

His former star players, David Beckham and Cristiano Ronaldo, were among those to voice support. Beckham wrote on Instagram:

Ronaldo, now at Real Madrid, said: “My thoughts and prayers are with you, my dear friend. Be strong, Boss!”

Ferguson had appeared fit and well when he presented his old sparring partner Arsène Wenger with a memento at Old Trafford last Sunday ahead of the Frenchman’s departure from Arsenal.

Two weeks ago he dined with Pep Guardiola, the manager of United’s local rivals, Manchester City, after the latter won the Premier League title.

Guardiola said he sent Ferguson “a big hug”. “Our thoughts are with Cathy and the Manchester United family,” he said. “I was glad to have dinner with him two weeks ago, and hopefully he can recover as quickly as possible.”

Outside Old Trafford, where Ferguson won 38 trophies and became the most successful football manager in the history of the game in Britain, fans expressed shock.

“I just couldn’t stop crying when I heard,” said Norma Smith, 73, a season ticket-holder for almost 60 years. “We’ve got our own chapel here at Old Trafford and I’ve been to church this morning to pray for him. Devastated, devastated.”

A stand at the ground was named in Ferguson’s honour in 2011 and a statue of the Glasgow-raised manager was erected of him in 2012. It gazes out towards Salford Royal hospital.

“I’ve been all over the world watching United and he’s brought me so much joy,” said Peter Bolton, 61. “He’s been retired a few years but he’s still the top man. Our life has been improved more than we could ever imagine. The bottom line is 38 trophies in English football, not Scottish football, or Spain or Germany – Fergie just knew what to do, how to do it and not only that, he did it.”

Facebook Twitter Pinterest Peter Bolton, 61, has been travelling around the world to attend Manchester United matches. Photograph: Josh Halliday/The Guardian

A brain haemorrage is a type of stroke that can be fatal and occurs when there is bleeding on the surface of the brain, just below the arachnoid membrane. It is most commonly caused by an aneurysm, which is a small, balloon-like swelling on an artery. The haemorrhage happens when the aneurysm wall bursts and blood escapes into the surrounding tissue, killing brain cells.

Contributing factors include smoking, high blood pressure and excessive alcohol consumption, but aneurysms can occur in people without these known risk factors. After a scan and medication to reduce the risk of secondary brain damage caused by reduced blood flow to the brain, surgery under general anaesthetic is often needed.

One method involves a neurosurgeon cutting a bone flap in the skull and sealing the aneurysm shut with a tiny metal clip that stays permanently clamped in place. Another involves passing tiny platinum coils through the vascular system from an incision in the groin, to seal off the aneurysm from the main artery.

There is a danger that the aneurysm can burst again or that brain damage has occurred. For survivors, memory and concentration are commonly affected and depression and anxiety can occur, while epilepsy develops in about one in 20 people. Headaches, tiredness and loss of sensation in other parts of the body during recovery are also common.