Jamaica dominated the sprint races at the Diamond League meet in Shanghai on Saturday, with Shelly-Ann Fraser-Pryce winning the women's 100 metres and Warren Weir capturing gold in the men's 200.
Fraser-Pryce, a two-time Olympic champ, ran 10.93 seconds to beat Blessing Okagbare and defending world champion Carmelita Jeter, who pulled up at the finish with an apparent leg injury.
Jeter fell to the track after the race and lay on her back for several seconds before being carried off on a stretcher. Meet organizers said the American would undergo tests to determine the nature of the injury.
Fraser-Pryce is off to a strong start this year. She also won the 200 in the season-opening Diamond League meet last week in Doha, Qatar.
"I feel very relaxed," she said. "I came here to win and just to see how I would do."
Weir, the bronze medallist at the London Olympics, finished in 20.18 seconds to hold off Justin Gatlin and Jason Young in the final few strides.
"I'm a bit jet-lagged so I wasn't expecting a very fast time," Weir said. "But I'm pleased with the time."
The field was weakened by the withdrawal of Olympic silver medallist Yohan Blake because of injury. Usain Bolt is also taking a break from the 200 to focus on the 100.
Gatlin, a 2004 Olympic gold medallist , followed up his win in the 100 in Doha last week with another strong performance in Shanghai. He returned to competition in 2010 after serving a four-year ban for doping.
"I'm just happy to be here, happy to be in Shanghai and going to other meets and to be able to participate," Gatlin said.
American Jason Richardson took gold in the 110 hurdles, crossing in 13.23 to edge Ryan Wilson and Xie Wenjun at the line. Olympic champion Aries Merritt pulled up before the first hurdle with what he later said was a leg cramp.
Olympic champion Kirani James of Grenada extended his dominance in the 400, comfortably beating American Leshawn Merritt in a time of 44.02.
"The focus for me this year is on the world championships and this is a strong beginning," James said. "We're looking at my performance here and going back to the drawing board to see what we can work on, see if I need to back off anything."
Asbel Kiprop of Kenya outsprinted Mekonnen Gebremedhin down the final stretch to win the men's 1,500, lunging across the finish line in 3:32.39, just .4 seconds ahead of the Ethiopian.
Russia's Yelena Isinbayeva won the women's pole vault in Shanghai for the fifth time with a leap of 4.70 metres, despite feeling pain in her take-off leg.
The two-time Olympic and world champion said she may take the rest of the summer off from competition if tests reveal a serious injury, with the hope of returning for the world championships in Moscow.
"I'll check with the doctor on Monday and he will tell me what I should do," she said.
China's Li Jinzhe was the surprise winner in the men's long jump with a leap of 8.34 metres, beating Russia's Aleksandr Menkov in second and Olympic champion Greg Rutherford of Britain in third.