A starry sky and the majestic Matterhorn mountain looming over a climber competing in the 22nd Glacier Patrol race in Ober Stafel, above Zermatt, Switzerland, on Wednesday.

The gruelling, high-altitude Glacier Patrol race (Patrouille des Glaciers in French), organised by the Swiss army, is regarded as the toughest of its kind in the world.

The route takes competitors - who must be able to climb and ski in inhospitable alpine environments - through the Valais Alps along the Swiss-Italian border from Zermatt to Verbier.

It takes place every two years, with this year's edition slated to end on Sunday, and draws civilian and military patrols from all over the world.

The event has its origins in military border patrols during World War II, with the aim of defending the south-western part of the Swiss Alps. However, subsequent races were marred by controversy over the deaths of competitors.

The organisers relaunched the contest in 1984.

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