Berlin - Linet Masai ended a 12-year title drought for Kenya with victory in the women's 10,000m while Usain Bolt exchanged smiles with another runner on his way to the 100m semi-finals at the world athletics championships on Saturday.

Masai took full advantage of the injury-related absence of two- time defending champion Tirunesh Dibaba to win a slow-paced race in 30 minutes 51.24 seconds.

She pipped Ethiopian season leader Meselech Melkamu (30:51.34) on the final strides, with Meseret Dafar of Ethiopia third in 30:51.95.

German President Roman Herzog officially opened the nine-day championships in the Olympic Stadium a few hours after Valeriy Borchin of Russia added the 20km walk title to his Olympic gold in the first final held in downtown Berlin. The day's other medal event was the men's shot put.

The three-time Olympic champion Bolt strolled through his second round race, easing up after little more than half of the distance and spending the remaining seconds exchanging smiles with Antigua runner Daniel Bailey.

Bailey won in 10.02 to Bolt's 10.03. Former world record holder Asafa Powell led the round with 9.95 seconds and Bolt's alleged principle rival Tyson Gay 9.98 after a terrible start due to his nagging groin problem.

"The groin is pretty sore," said Gay, who limped out in the Olympic semi-final last year. "But it went pretty well."

Bolt, clearly enjoying his star status by working the crowd, had nothing to say while Powell, who has always chocked in big finals, was happy to have survived a morning scare in the heats when he eased up too soon and was almost eliminated.

"It feels good. I just wanted to get out of today," said Powell.

The 100m culminates on Sunday with the semi-final and final as the highlight of the championships, with expectations high that Bolt can better his world record of 9.69 seconds from last year.

In the women's 10,000m, the late withdrawal of Defar did not seem likely to stop Ethiopia from winning, but neither Melkamu nor Defar could stop Masai on the home stretch.

Wude Ayelew led a five-strong leader group onto the final straight, but then tired dramatically to finish fifth.

Melkamu took the lead but Masai gave everything she had and passed her on the outside for a stunning win, Kenya's first over the distance after five Ethiopian titles since Sally Barsosio won in 1997.

Borchin, 22, shook off Chinese rival Hao Wang shortly after the 15km-mark as he claimed victory in 1 hour 18 minutes 41 seconds on a sunny midday in downtown Berlin.

Hao got the silver in a personal best 1:19:06 hours and Eder Sanchez of Mexico took the bronze in 1:19:22.

An early leader group of Italians Giorgio Rubino and Ivano Brugnetti and Norwegian Erik Tysse could not maintain the pace in the second half of the race.

"I was trying to prevent the other athletes from going too far away from me. The most important thing was not to leave the group," said Borchin about the crucial first half of the race.

In the men's 1,500m heats defending champion Bernard Lagat of the US advanced into the semi-finals in 3:41.60 minutes along with Kenyan Asbel Kiprop, who won the same heat in 3:41.42 minutes.

Kiprop, 20, claimed Olympic silver, but could be declared gold medallist if the suspended original winner in Beijing, Rashid Ramzi of Bahrain, is confirmed to be a doping offender after being caught in retests using the latest generation of the blood booster EPO.(dpa)