Kenya's Faith Kipyegon produced a startling last-lap sprint to outpace favourite Genzebe Dibaba of Ethiopia to win the Olympic women's 1500m gold.

Kipyegon clocked 4min 08.92sec after her burst over the last 250 metres, world record holder Dibaba taking silver in 4:10.27.

American Jennifer Simpson claimed bronze in 4:10.53.

"I knew it would be a fast race, I really had to kick on the last lap," asid Kipyegon.

"I was well prepared for the race. I'm proud to win for my country."

"It's just amazing, I'm very happy because it's my first medal in the Olympics.

"It was a good race, a tactical race."

Dibaba broke the world indoor mile record and won the world indoor 3000m title at the start of the year, but had to delay the start to her outdoor campaign with a toe injury.

The Ethiopian, who also made headlines when her Somali coach SJama Aen was arrested in Spain as part of a drugs-trafficking investigation, blamed her performance on lack of track time.

"I had some injuries in the last month and I was not able to train as hard as usual," she said.

"I had a fierce competitor in Faith and I'm happy with my result."

American Shannon Rowbury and Britain's Laura Weightman, who competed in the notorious 1500m at the 2012 London Games from which six of the top nine finishers have since been disqualified for doping, took up the early pace and it was slow.

With two laps to go at the Olympic Stadium, world champion Dibaba surged to the front, the field immediately strung out with the added pace.

Dibaba held her lead through the bell for the final lap, but was expertly reeled in with under 250 metres to go by Kipyegon.

The 22-year-old Kenyan, who won silver behind Dibaba at last year's world championships in Beijing, pulled level with the Ethiopian and then away from her in an incredible display of finishing.

Dibaba began to tie up as the line approached.

But the 25-year-old just managed to hold on for silver from 2011 world champion Simpson, whose bronze was the United States' first Olympic medal in this event.

"I love competing," said Simpson. "I love feeling that stress on the last lap.

"I was one of the crowd who could maybe get third so I'm really happy."

The women's 1500m at the London Games has gone down in history as the race in which six of the top nine athletes were disqualified for doping violations.

The IOC is still debating whether they should re-allocate the medals for that race.