Olympic heptathlon champion Jessica Ennis-Hill has withdrawn from next month's athletics world championships because of injury, she and her coach said on Wednesday.

Ennis-Hill was provisionally named in the Great Britain squad on Tuesday for the competition in Moscow from August 10-18, despite struggling with an Achilles problem.

But her coach, Toni Minichiello, was quoted as saying by the BBC website: "In the last 24 horus we have looked at her Achilles injury and it has not responded well enough, so the decision is to withdraw her from the World Championships."

Ennis-Hill, 27, was one of the stars of the London Olympics last year and her victory in the seven-event competition made her one of Britain's most recognisable sports stars.

She competed at last weekend's Diamond League/Anniversary Games meeting at the Olympic Stadium in east London with her ankle heavily strapped and finished fourth in the 100m hurdles.

She was also quoted as saying by the BBC: "To say I am gutted is an understatement -- no athlete likes to miss the opportunity to compete at a major Championships -- they don't come round that often.

"Up until now we have been focusing on managing the pain so I can train and get myself in shape to go out there to win in Moscow -- which has meant not focusing on finding a cure for the injury.

"The time has now come to stop chasing fitness and look to cure the problem."

Ennis-Hill is the latest high-profile withdrawal from the world athletics championships, after Olympic 800m champion David Rudisha of Kenya also pulled out through injury.

Sprint events have been hit after Jamaica's Asafa Powell and US runner Tyson Gay -- two of the fastest men ever over 100m -- tested positive for banned substances.

Jamaican ace Usain Bolt's training partner and the reigning world champion at the distance, Yohan Blake, has withdrawn with a hamstring injury.