An avalanche on Tuesday swept away two-time world extreme snowboard champion Estelle Balet to her death in the Swiss Alps, police said.

The 21-year-old Balet, who had won her second straight title on the Freeride World Tour only two weeks ago, was making a film when she was killed, Swiss police said in a statement.

Balet was speeding down a slope near the resort of Orsieres on her snowboard when the avalanche started and carried her away, police added.

Another snowboarder had been on the slope just before Balet passed.

The Swiss woman was wearing a tracking device, an airbag and was wearing a helmet.

Rescuers managed to dig her out of the snow, but police said: "Despite an attempt to resuscitate her, she died at the scene of the accident."

"I feel a huge sadness, a feeling of bitterness and above all solidarity with her family and friends," Nicolas Hale-Woods, founder of the Freeride World Tour, told AFP.

"It is a reminder that no matter how well prepared you are, taking part in freeride in the mountains has an element of uncertainty," he added.

Balet came from the Valais region of Switzerland and had been snowboarding since the age of 10. She had been on the Freeride World Tour since the junior level.