Five people were killed and a sixth seriously injured after a climbing accident Sunday morning in the Austrian Alps, rescue services said.

The cause of the accident, which occurred below the Mannlkarscharte pass near Zell-am-See, about 80 kilometres (50 miles) south of the central city of Salzburg, has not yet been determined.

"We think a rope may have come loose," said Anton Voithofer, head of the Red Cross rescue team.

Five helicopters were sent to the scene, and the injured climber was transported to a hospital in Schwarzach.

The victims have not yet been identified.