Formula 1: Alonso, Massa and Vettel send prayers and wishes to injured Michael Schumacher

The German Formula 1 legend, who will be 45 on January 3, is in a critical condition in a hospital in Grenoble and medics fear for his life.

“Come back soon, Michael! I hope to hear positive news about you soon!” world number two Fernando wrote on his Twitter.

His former team-mate on Ferrari, Brazil's Felipe Massa, wrote on Instagram: “I'm praying to God to protect you, brother, and for you to get better quickly,” and uploaded a photo of the injured driver hugging him.

Schumacher's compatriot Sebastian Vettel, reigning world champion for Red Bull, described his 'utter shock' at the news of his childhood hero's accident.

“This is the most important race of your life, and you're going to win it,” said an emotional Vettel.

He said Schumacher had been 'like a father' to him over the course of his Formula 1 career.

“Michael has been with me, by my side, at every stage,” Vettel lamented.

Spokeswoman for Schumacher's family, Sabine Kehm, has called for 'privacy' for his nearest and dearest, and confirms his accident was purely that, there was nobody else involved, but he was not alone at the time.

She asked for the public to 'be understanding' and not to expect 'constant updates' on the racing driver's condition.

Michael Schumacher's doctors in intensive care at Grenoble hospital says the driver's life 'is in great danger' and they are unable to say whether he will survive.

Although said to be conscious upon arrival and, initially, not thought to be at serious risk, his condition worsened over the next 24 hours and he is said to be in a medically-induced coma.

Neurosurgeon Dr Stéfan Chabardes revealed that Michael Schumacher had undergone emergency surgery for bruising to and fluid on his brain and that to help prevent damage caused by inter-cranial pressure, his body temperature has been clinically reduced to a level of hypothermia – between 34ºC and 37ºC.

Schumacher had been skiing off-piste with his 14-year-old son at the Méribel resort, where he owns a holiday home, at 11.000hrs on Sunday when he suffered a fall, hitting his head on a rock.

Such was the impact that his crash helmet split, but so far it has saved his life – Dr Chabardes says without it, he would certainly have died.

He was said to have fallen into a coma as a result of the fall and was rushed to theatre upon arrival at Grenoble university hospital and is said to have suffered inter-cranial bruising, although other reports described this as a 'haemorrhage' and the severity of the bleeding is not clear.

A second operation is not likely to be needed, say hospital staff, but his life is hanging in the balance.

When first admitted to hospital, the racing driver was said to be conscious and the injury 'not too serious', but he quickly went downhill.

His wife Corinna and his two children are keeping a bedside vigil.