Felix wins 11th world title, Jiayu wins China's second gold

American Allyson Felix took her 11th world career gold medal at the IAAF World Championships while Yang Jiayu won the women's 20km race walk to earn China their second gold medal.

Usain Bolt, who suffered a shock injury on Saturday night's 4x100m relay, stole the highlight again as he appeared on the track and was presented with a framed piece of the London 2012 Olympic track by IAAF President Sebastian Coe and London Mayor Sadiq Khan.

He then walked a lap of honour to the roar of the sell-out crowd of 70,000 at the London Olympic Stadium. The emotional Jamaican super star waved to fans and finally stroke a few trademark poses.

Yang's victory in her first world championships surprised all including her better-known teammate Lyu Xiuzhi, the Rio Olympic bronze medalist and Beijing worlds runner-up. Lyu, apparently eager to catch up, was disqualified meters from the finish line.

"I feel really excited," said Yang, 21. "I started race walking at the age of 14. Now I hope to be the future of race walking in China."

Earlier in the women's 50km walk, a pair of unknown Chinese athletes became the surprising medalists as Yin Hang won the silver in an Asian record time of 4:08:58 and Yang Shuqing set a personal best of 4:20:49 to bag the bronze.

The three walkers helped China climb to fifth on the final medal standings with two golds, three silvers and one bronze, behind the United States (10-11-9), Kenya (5-2-4), South Africa (3-1-2) and France (3-0-2).

Felix, 31, clocked 48.7 seconds in the second lap to lead the US quartet to the title in the women's 4x400m relay. Of her 16 world medals, 11 have been gold, while nine in total were won as part of the US relay team and seven individually. She has also won nine Olympic medals including six golds.

Elsewhere, Kenya's Hellen Obiri upset defending champion Almaz Ayana to win 5,000m gold. Kenya also finsihed a one-two in the men's 1500m as Elijah Manangoi held off Timothy Cheruiyot.

Mutaz Barshim, Qatar's Olympic silver medallist, won the men's high jump gold with a jump of 2.35m. Russia's Danil Lysenko took silver ahead of Syria's Majd Eddin Ghazal in third.

Double Olympic champion Sandra Perkovic of Croatia claimed the women's discus gold medal with a throw of 70.31m.

South Africa's Caster Semenya, the Olympic champion, won easily the women's 800m in a personal best one minute 55.16 seconds, the fastest time in the world for nine years.