The 100th edition of the Vierdaagse, a four day walking event centred on Nijmegen, started in the early hours of Tuesday morning with 47,166 walkers.

Civilians and soldiers from 68 different countries are taking part in the marches, which involve walking 30, 40 or 50 kilometres every day for four days. They range in age from 11 to 93.

The walk had been open to 50,000 people but some 2,000 failed to show up to collect their starting documents, the organisers said.

This year, walkers are being urged to be sensible in the heat, which is set to top 30 degrees on Tuesday and be even hotter on Wednesday.

In 2006 the event was cancelled after two walkers died of heat stroke.

Key facts about the Vierdaagse