Eight yachts representing seven nations set off Saturday from the Spanish Mediterranean port of Alicante on the Volvo Ocean Race around the world, one of the most gruelling and hazardous events in sport.

Thousands of people and hundreds of spectator boats saw the competitors off around 2pm (2300 AEDT) under cloudy skies and in the presence of Spain's King Juan Carlos.

The 10th edition of what started in 1973 as the Whitbread race is the longest and most challenging ever, and includes three stops in Asia for the first time - in Cochin in India, Singapore and Qingdao in China.

After 37,000 nautical miles (68,500km), the finish line is in St Petersburg, Russia, where the teams are expected in June 2009.

The 88 sailors on the eight 70-foot (21.5m) single-hull yachts already face a challenging first two days as they head toward Gibraltar, where stormy weather drove two freighters aground during the night.

From there, they travel south across the Atlantic to the first stop in Cape Town, South Africa, where they are expected around November 3.

Sweden's Ericsson Team International, skippered by Brazil's two-time Olympic gold medallist Torben Grael, and Spain's two Telefonica yachts are the favourites.

But US entry Puma Ocean Racing and the Sino-Irish Green Dragon are seen as strong outsiders.

As the yachts headed out of Alicante bay into the open sea, Ericsson was leading Puma and Telefonica Blue.

The race is expected to be tighter than ever, with the toughest leg that between Singapore and Qingdao, followed by the longest stage, between Qingdao and Rio round Cape Horn.

The teams are "much better prepared" than before and the yacht designers have "homogenised the fleet," said French yachtsmen Sebastien Josse.

Josse took part in the last Volvo race in 2005-06 aboard the Dutch boat ABN-Amro II, on which a crew member died after being washed overboard. The boat later rescued the crew of the Spanish yacht Movistar after their boat sank.

The three other teams competing are Ericsson Team Nordic, which has already been penalised for a rules violation over the weight of its keel, and Team Russia and Team Delta Lloyd from the Netherlands, which have repaired damage to their boats following a collision during the in-port race in Alicante.

Each of the yachts receive points according to their position in each of the 10 legs. Half points are also awarded at seven "scoring gates" along the route and for the seven "in-port" races.

On October 4, Telefonica Blue, skippered by Dutch veteran Bouwe Bekking, took an early lead in the competition by winning the first of seven "in-port" regattas.