BERLIN (AFP) - Formula One legend Michael Schumacher was not skiing at high speed when he suffered a severe accident, his manager said on Tuesday, blaming instead a "chain of unfortunate circumstances".

Schumacher was skiing "with a small group of friends" as well as his 14-year-old son Mick, his manager Sabine Kehm told journalists at the Grenoble Hospital where he is being treated.

In the accident, "apparently the helmet broke", she said.

"That doesn't mean that Michael was travelling at high speed. He seems to have hit a rock as he took a turn. It was a chain of unfortunate circumstances."

Ms Kehm added that the accident could have happened even "at 10 kilometres per hour" and took place during "a normal turning manoeuvre".

Several media reports have suggested that he was skiing at high speed at the time, with some saying he could have been going as fast as 60 to 100 kmh.

Germany's top-selling Bild newspaper quoted her saying that Schumacher was only gathering speed at the time, having apparently just helped a skiing companion to his feet after a fall.

"Michael was skiing on a normal piste with the group," Ms Kehm was quoted saying. "Nearby was an area of deep snow. Michael skied into it. He wasn't going fast because he had apparently just helped a friend who had fallen down.

"So Michael just got going again, skied into the deep snow and then - we suspect - hit the rock as he entered a curve.

"Michael was not going very fast. But unfortunately as he took the turn, we assume, he hit the rock and was catapulted upwards and then struck a rock head-first."