An operation is under way to parachute medical help to four sailors who were injured when a large wave crashed onto their yacht during a round-the-world race.

Three British crew members and one Australian were hurt on board the vessel, which is currently 400 miles off the California coast in the Pacific Ocean.

They suffered a range of injuries - including suspected broken ribs - when a wave hit the boat in storm conditions on Saturday, sweeping away its steering wheel and mount and some of its communications equipment.

The boat, the Geraldton Western Australia, is one of 10 UK registered 68-foot yachts competing in the Clipper Round The World Yacht Race, which takes place once every two years.

Race organisers Clipper Ventures said the injured crew include Jane Hitchens, a 50-year-old doctor from Kent, who has four suspected broken ribs, and Mark Burkes, 37, from Worcestershire, who has suffered a back injury.

The others were named as Nik Brbora, a 28-year-old software engineer living in London, who has possible pelvic sprain, and 62-year-old Max Wilson, from Queensland, Australia, who has two suspected cracked or broken ribs.

The rest of the 18-strong crew are said to be uninjured but shaken by the incident and those who are medically-trained have treated the four injured crew members.

The 40,000-mile race, which features predominantly amateur crews, began on July 31 in Southampton and will finish there in July this year. Crews began the current leg, which covers 6,000 miles from China to California, in early March.

The US coast guard said medical supplies had been dropped on to the yacht, but poor weather conditions meant paramedics were unable to jump out of the aircraft.

Explaining the revised plan, coast guard spokesman Levi Read said a coast guard ship had been sent towards the yacht, with a long-rage helicopter set to take off from it once it is within range. A medic will be lowered onto the boat and can evacuate people if necessary, he said.