Gao Xinglong wins the fourth place during the Beijing 2015 IAAF World Championships at the National Stadium, August 25, 2015. [Photo/IC] Gao Xinglong, 21 Awards: Bronze medal 2014 Incheon Asian games Gold medal 2014 National Indoor Championships

Bett put on a strong performance to run the world leading time as 23-year-old he had never broken 49 seconds at sea level.

In women's events, Cuban discus thrower Denia Caballero beat Croatian Sandra Perkovic for the second time in the year and denied the latter's effort to win her second consecutive world title as she nailed the gold medal on her first throw of 69.28 meters.

Perkovic had to settle for the silver on 67.39m while German Nadine Muller came third in 65.53.

The 25-year-old Perkovic just lost four times in three years she has tasted defeat only four times but her loss to Gaballero hinted the upset in Beijing.

Genzebe Dibaba of Ethiopia clocked 4:08.09 to win the women's 1,500m gold medal and Faith Chepngetich Kipyegon of Kenya claimed silver in 4:08.96. Sifan Hassan of the Netherlands took bronze in 4:09.34.

Bolt, who just defended the 100m title on Sunday, strolled to qualify for the 200m semifinal in 20.28 seconds.