Ruth Chepngetich won the first title of the World Athletics Championships the women's marathon in a gruelling race that saw many of the pre-race favourites fail to finish as fierce heat and humidity took their toll.

The 25-year-old world number one timed 2hrs 32 minutes 43 seconds in a race whose arduous nature was reflected in all three of the Ethiopians failing to make it past the halfway mark -- the trio among around a couple of dozen who found the going too tough.

Some had to be stretchered off, with Linet Chebet of Uganda taken away in an ambulance and Italy's Sara Dossena wheeled away in a wheelchair.

Defending champion Rose Chelimo of Bahrain took silver and Namibia's Helalia Johannes the bronze in a race in which the runners received water bottles wrapped in ice with Israel's 10,000 metres champion Lonah Salpeter at one point taking a cap with ice in it to cool her down.

"I was not expecting to be a medallist in such tough conditions," said a smiling Chelimo.

"Here was much hotter than Jakarta (where she won the Asian Games title last year)," she added.

Kenyan-born Salpeter, who moved to Israel as a nanny for a Kenyan diplomat and subsequently married her Israeli coach, dominated the early part of the race leading Chepngetich, another Kenyan Visiline Jepkesho, Chelimo and Ethiopian Ruti Aga in fourth.

Chepngetich -- who is the third fastest woman in marathon history -- blew the group apart with a sudden surge with only Aga, Chelimo and Jepkesho able to go with her.

Salpeter lost valuable ground when she dropped her water bottle at a drinks station and stopped to pick it up.

Chepngetich set an astonishing pace with only 13km gone watched by a fair sized crowd gathered round the Corniche.

One of the pre-race favourites Ethiopia's Rosa Dereje, who was third in this year's London marathon, dropped out with an ankle injury shortly before the 15km mark.

She was one of several who pulled out around that mark, Dossena, Ukraine's Oleksandra Shafar and Clementine Mukandanga all calling it a night.

Oblivious to the growing carnage behind her, Chepngetich briefly opened up a gap but was joined by Kiplagat, Chelimo, Jepkesho and Namibian Helalia Johannes -- they held a 55 second lead over Salpeter at the 15km mark.

Ethiopia suffered another blow when Aga found the going too hot for her and came to a halt being led away disconsolately by a team official.

Ethiopia's misery was complete when Shure Demise gave up the ghost before the 20km mark.

Salpeter appeared to have regathered her composure as she reduced the gap between her and the leading quintet from 55 seconds to 11sec with 24km gone.

However, that was as close as the Israeli got as the lead quartet pulled away again -- they dropped Jepkesho -- to battle for the medals amongst themselves.

Chepngetich made a break for glory as the bell went leaving her three rivals trailing in her wake -- Chelimo giving chase but Johannes and Kiplagat's chances of winning had gone.

Chepngetich never allowed Chelimo a sniff of a chance and strode imperiously to victory to give Kenya their fifth gold in the event.