Jamaican sprinter Usain Bolt has resumed his quest for more gold at the London Olympics, after successfully defending his title as the world's fastest man.

Bolt returned to competition Tuesday, fresh off his victory in Sunday's 100-meter finals. Bolt advanced to the semifinals of the men's 200 meter sprint, along with teammate Yohan Blake, the 100-meter silver medalist.

The story was different for Chinese hurdler Liu Xiang. The 2004 gold medalist in the 110-meter hurdles hit the first hurdle in that event, crashed to the track and had to be carried off. In 2008 at the Beijing Games, Liu was forced to withdraw due to a foot injury.

Meanwhile, host country Britain added to its fast-growing medal tally Tuesday.

Alistair Brownlee won gold in the men's triathlon, pulling away from silver-medal winner Javier Gomez of Spain halfway through the last leg of the event, the 10-kilometer run.

Brownlee's teammate and younger brother, Jonathan Brownlee, claimed the bronze.

And China earned two more gold medals in gymnastics. Deng Linlin, a world champion on the balance beam in 2009, finished first on that apparatus. Earlier, China's Feng Zhe captured the men's parallel bars title.

China and the United States are far ahead in the medal count, each with more than 60. Britain and Russia are about tied for third in total medals, but Britain has twice as many gold medals.