Seven-times Formula One world champion Michael Schumacher was fighting for his life on Monday after suffering severe head injuries in a skiing accident in the French Alps resort of Meribel, doctors said.
"We can say that his condition is life-threatening," Jean-Francois Payen, head anaesthetician at the CHU hospital in the eastern French city of Grenoble, told a news conference.
"For the moment we cannot say what Michael Schumacher's future is," he added. "We are working round the clock - we are trying to win time."
The retired motor racing great, 44, slammed his head on a rock while skiing off-piste on Sunday morning in the French Alpine resort where he has a vacation home.
"His helmet did of course protect him at least partly. Someone who had suffered a similar accident without a helmet would not have made it here (to the hospital)," Payen said.
Philippe Quincy, the Albertville public prosecutor, told Reuters an inquiry had been launched on Sunday to identify the causes of the accident. Initial findings indicated the blow was so hard that Schumacher's helmet had shattered.
"We know that the accident took place in an off-piste zone where rocks were partly or totally hidden by snow," Quincy said, adding that Schumacher had likely been thrown off balance by one of them.
Schumacher was initially conscious as he was transported to a local hospital in Moutiers and then to Grenoble. However, his condition deteriorated sharply afterwards.
Neurosurgeon Stephan Chabardes said an emergency brain scan carried out on Schumacher had revealed internal bleeding and injuries including contusions and lesions. He said they had operated to treat the internal bleeding.
Doctors said Schumacher had been placed in an artificial coma but, contrary to an earlier French media report, said they had not carried out a second operation during the night and were not planning any further interventions at this stage.
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A spokesman for German Chancellor Angela Merkel said she was shocked to hear the news.
"We hope that he overcomes his injuries and can recover," the spokesman told a regular briefing in Berlin.
Hopes and prayers
In Germany, Schumacher's accident topped news bulletins, with the bestselling tabloid newspaper Bild reporting on its website: "Schumi fighting for his life".
Schumacher is under the care of Professor Gerard Saillant, a brain and spinal injury expert who is also president of the International Automobile Federation (FIA) Institute. Saillant told the news conference he was there as "a friend" and gave no further details on his condition.
Bild reporters said Ross Brawn, the Briton who worked with Schumacher at Ferrari and Mercedes as technical director and team principal respectively, had arrived in Grenoble.
Leading names in motor racing reacted with shock on Twitter.
"If anyone can pull through, it's him," said Britain's triple Indy 500 winner Dario Franchitti, who is still walking on crutches after a crash in October that ended his racing career.
"Come on Michael, give us one of those race stints at pure qualifying pace to win through, like you used to. You can do it," said Schumacher's former Benetton team mate Martin Brundle.
Former Ferrari team mate Felipe Massa, who suffered a near fatal head injury at the 2009 Hungarian Grand Prix, said he was praying for his friend.
Red Bull's quadruple world champion Sebastian Vettel, Schumacher's friend and compatriot, expressed his shock and support for the family.
Schumacher is the most successful Formula One driver of all time with a record 91 race victories in a career spanning more than two decades.
He won his first two titles with Benetton in 1994, the year when Brazilian triple champion Ayrton Senna died in a crash at the San Marino Grand Prix, and 1995.
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The German then took five in a row with Ferrari between 2000 and 2004 in what now seems a golden age for the Italian team who named a square after him outside Enzo Ferrari's old house at their Fiorano test track.
Schumacher left the sport last year after a less successful three-year comeback with Mercedes following an earlier retirement from Ferrari at the end of 2006. He lives in Switzerland with his wife and two children.