Formula One legend Michael Schumacher is fighting for his life in hospital after sustaining serious head injuries in an off-piste skiing accident at a resort in the French Alps on Sunday morning.

Schumacher, 44, was airlifted to Grenoble after falling heavily and hitting his head while skiing on the unmarked slope at the Méribel resort with a group of friends and his 14-year-old son.

After hours of silence which raised worldwide concerns about the seven-time former world champion's condition, the Grenoble hospital issued a statement on Sunday night describing his state as "critical". He was in a coma on arrival at the hospital suffering from "severe brain trauma" and had undergone surgery, the statement said. French media reports said that Schumacher, whose family is at his bedside, had also had a brain haemorrhage.

The hospital statement was issued more than three hours after the Grenoble-based newspaper Le Dauphiné Libéré reported that Schumacher's injuries had worsened and were now "life threatening".

A top brain surgeon from Paris, Gérard Saillant, rushed to the hospital to attend to the former grand prix driver. Saillant, an expert in brain and spine injury, is a close friend of Schumacher, having operated on him when he broke his leg at Silverstone in 1999.

Radio Monte Carlo reported that doctors would provide an update on Schumacher's condition at a press conference at the hospital at 10am GMT on Monday.

A skier with Schumacher's group raised the alarm within minutes of the accident which occurred just after 11am in bright and sunny weather. "The skier alerted mountain rescue just a few hundred metres below where he fell," said the director of Méribel Alpina, Olivier Simonin, in charge of security and skilifts at the site. Two rescuers arrived quickly at the scene and called in two others to help evacuate Schumacher who had been wearing a helmet at the time of the accident. Schumacher remained conscious after the fall and was initially helicoptered to the nearest hospital at Moûtiers. But doctors had then him flown to Grenoble, which has a specialised trauma unit.

Michael Schumacher was skiing on an unmarked slope with his 14-year-old son at the Méribel resort. Photograph: Sipa Press/REX

Simonin said it was not known whether Schumacher hit his head on a rock. "All we know is that he hit his head," he said.

The hospital announcement was the first since a terse statement in the afternoon released by Schumacher's manager, Sabine Kehm. She confirmed the accident and said that nobody else was involved in the fall.

"Michael fell on his head when he was on a private skiing trip in the French Alps. He was taken to hospital and is receiving professional medical attention. We ask for understanding that we cannot give out continuous information about his health," the statement said.

Méribel director Christophe Gernignon-Lecomte had earlier described Schumacher as being "in shock, somewhat shaken, but conscious" when the emergency rescue team reached him. He also said that Schumacher's head injury was "not serious", but a resort spokesman said later that the Méribel officials were waiting for a more comprehensive medical report.

Gernigon-Lecomte said that Schumacher owned a chalet in the valley and knew the resort and the pistes of Méribel well. "It was something habitual for him," he said.

French media said in the afternoon that the sportsman's cranial trauma was not life-threatening. However, by early evening, that prognosis changed, and Formula One champions such as Felipe Massa said they were praying for Schumacher. Some French fans of Schumacher gathered in the afternoon outside the hospital, as they waited in vain for news. Olivier Panis, a former Formula 1 driver from Grenoble, came to the hospital twice during the day but was unable to see the German driver.

When he fell, Schumacher was skiing close to one of the chic resort's most difficult pistes in the Three Valleys enjoyed by the world's most accomplished skiers. Méribel, where the Swiss-based former champion owns a chalet, is one of the top ski resorts in the French Alps.

He was skiing off-piste between the pistes La Biche and the more difficult runs of Mauduit, named after the former French skiing champion George Mauduit. The slope, devoid of trees, where he and his son were skiing, is at an altitude of 2,100 metres, close to the luxury resort of Courchevel. The pair were about 20 metres away from the marked slope when Schumacher tumbled, according to Simonin.