Henze was on his way back to the Olympic village, along with another team official, when the accident occurred.

Germany's Olympic Sports Confederation (DOSB) confirmed that Henze had suffered a serious head injury, and that the doctors say his injuries were life-threatening. He was admitted to hospital for emergency treatment, and was then transferred to another hospital, where he was operated on.

"He is not well," said Germany's Head of Mission to the Rio Olympics, Michael Vesper. "Stefan's in our thoughts and we hope he can win this battle."

Henze is a former slalom canoeist, who won silver at the 2004 Olympics in Athens.

The other passenger in the car at the time of the accident, sports scientist Christian Käding, was lightly injured and was already released from hospital. "(Käding) is doing well under the circumstances," the DOSB said.

ftm/rc (dpa/AP)