BEIJING (AP) — The Latest from the world championships (all times local):

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10:15 p.m.

Wayde van Niekerk left the Bird's Nest in an ambulance after winning the 400-meter final at the world championships.

South African team leader Peter Lourens says van Niekerk "is OK. It's exhaustion. They are taking him to hospital for observation."

The 23-year-old van Niekerk won his first world title Wednesday, holding off defending champion LaShawn Merritt and Olympic gold medalist Kirani James.

Van Niekerk won in 43.48 seconds.

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9:30 p.m.

Wayde van Niekerk won his first world championship title in the 400 meters on Wednesday, holding off defending champion LaShawn Merritt and Olympic gold medalist Kirani James.

The 23-year-old South African went out hard and held on to win in 43.48 seconds. Merritt took silver in a personal best 43.65 and James finished third in a season-best 43.78.

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9:15 p.m.

Hyvin Kiyeng Jepkemoi of Kenya won a three-way sprint to the line to take the gold medal in the 3,000-meter steeplechase ahead of Habiba Ghibri of Tunesia and Gesa Krause of Germany.

Over a tight last lap, Ghribi stumbled ahead of one barrier and once the last water pit was passed, the finishing kick made the difference with Jepkemoi coming from behind to win in 9 minutes, 19.11 seconds.

Ghribi got silver, .13 seconds behind, and beat Krause by .01.

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9:10 p.m.

Yarisley Silva of Cuba cleared 4.90 meters on her third attempt in the pole vault to secure her first world championship.

Silva was a silver medalist at the 2012 London Olympics, missing out on gold in a countback.

Fabiana Murer of Brazil, the 2011 world champion, held the lead when she cleared 4.85 at her first attempt but missed all three attempts at the next height.

Nikoleta Kyriakopoulou of Greece missed her first attempt at 4.85 and, with a bronze medal guaranteed, passed her next attempt at that mark and moved to the next height but failed twice more.

American teammates Jenn Suhr, the Olympic champion, and Sandi Morris finished in a share of fourth place after failing to clear 4.80.

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8:48 p.m.

Usain Bolt slowed down halfway along the straight and coasted to win his 200-meter semifinal heat in 19.95 seconds, staying on track for a 100-200 sprint double at the world championships.

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8:40 p.m.

Justin Gatlin won his 200-meter semifinal heat in 19.87 seconds Wednesday to qualify automatically for the world championship final, where he's aiming to go one better than his silver medal in the 100.

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8:30 p.m.

Veronica Campbell-Brown rounded the curve in the 200 and kept going and going, straight into the next lane.

The Jamaican started in Lane 5 and wound up in Lane 6 at the world championships Wednesday. She won her heat, but running out of your lane leads to disqualification.

British sprinter Margaret Adeoye was shocked to see Campbell-Brown suddenly appear in front of her.

Campbell-Brown, the 2011 world champion in the event, didn't stop to talk after her mistake, saying she was, "having a headache."

The presence of Campbell-Brown nearly gave Adeoye a migraine, thinking she may have messed up.

"I was like, 'Was that me or was that her?'" said Adeoye, who finished third in the heat. "It helped me get to the finish line, so it's fine. I just wanted to get as close to her as possible, because I knew she'd probably get DQed."

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8:20 p.m.

Julius Yego of Kenya recorded the longest javelin throw in 14 years with a mark of 92.72 meters to win his first world championship gold medal on Wednesday.

Yego was in eighth position before his third attempt in the final, when he landed chest-down behind the line after unleashing the world-leading throw.

The world record of 98.48 meters was set in 1996 by Jan Zelezny of the Czech Republic, who also set the championship record at 92.80 in 2001.

It was the first time in history five throwers recorded marks beyond 87 meters in a championship final.

Ihab Abdelrahman El Sayed of Egypt briefly held the lead at 88.99 and finished with the silver medal. Tero Pitkamaki of Finland, the 2007 world champion, took bronze at 87.64, followed by Thomas Roehler of Germany (87.18) and Antti Ruuskaen of Finalnd (87.12).

The 26-year-old Yego entered the meet with a pesonal best of 91.39, the world-leading mark of the year.

Yego was the first Kenyan to reach an Olympic final in a field event at the 2012 London Games, the same year he won an IAAF scholarship to train in Finland.

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8:15 p.m.

Zuzana Hejnova of the Czech Republic defended her world title in the 400-meter hurdles on Wednesday with a world leading run of 53.50 seconds.

Hejnova came back strongly after missing the 2014 season after breaking a bone in her left foot.

Shamier Little of the United States got silver from the tight inside lane .44 seconds behind the Czech, edging teammate Cassandra Tate, who finished in 54.02.

Commonwealth champion Kaliese Spencer of Jamaica stumbled early in the race and finished last.

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7:40 p.m.

Julius Yego of Kenya recorded the longest throw in 14 years in the javelin with a mark of 92.72 meters with his third attempt in the final of the world championships on Wednesday.

The 26-year-old Yego entered the meet with a personal best of 91.39.

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6:50 p.m.

The IAAF says two Kenyan runners have tested positive for doping at the world championships.

Joyce Zakary, a 400-meter runner, and hurdler Koki Manunga tested positive for unspecified substances in targeted tests after competing in Beijing.

Zakary was second in her opening heat on Monday, running a national record of 50.71 seconds in the 400. But the 29-year-old Kenyan did not run in the semifinals a day later despite having the eighth best qualifying time.

Manunga ran in the opening heats of the 400 hurdles on Sunday and finished sixth of seven, failing to reach the semifinals.

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12:40 p.m.

Olympic finalist Alysia Johnson Montano was in the leading bunch when she tripped and tumbled to the track with 200 meters to go, ending her chances of advancing in the 800 at the world championships.

Montano, who always competes with a flower in her hair, got up and finished in 2 minutes, 9.57 seconds. She appealed against the result, saying she had been obstructed and should be advanced to the next round, but the IAAF rejected the protest after reviewing video of the race.

"It was just a big move that happened. I kind of had a little bump on the inside, so I moved myself over. I was clipped and went down," the 29-year-old American said. "That's all I know."

Montano placed fifth at the 2012 Olympics and fourth at the 2013 world championships in Moscow.

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12:05 p.m.

Abdullah Al-Qwabani came to the Bird's Nest to take on the best in the world, and did it in bare feet.

The 16-year-old Yemeni ran 12 1/2 laps on the synthetic track without shoes and recorded a personal best time of 16 minutes, 2.55 seconds. He was a distant last among the 39 runners who finished in the two heats of the 5,000 meters at the world championships.

But he did get to rub shoulders with some of the biggest names of the event, racing in the same heat as Olympic 5,000- and 10,000-meter champion Mo Farah, who was second-fastest of all those advancing in 13:19.44.

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11:40 a.m.

American hurdler Ronnie Ash disputed his disqualification in the second heat of the 110-meter hurdles at the world championships on Wednesday, and lingered behind for several minutes after being ordered to leave to leave the track.

Ash appeared to move when the field was set in the blocks and the red flag was waved. He stayed in his lane until officials confirmed he had to leave.

When he did leave to the rear of the start area, he was stopped by ushers who refused to let him back in the tunnel under the stadium, further delaying his exit.

Czech hurdler Petr Svoboda was disqualified for a false start when the field was re-set, meaning lanes three and six were empty when the heat eventually started.

Pascal Martinot-Lagarde won the heat in 13.35 seconds.

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11:25 a.m.

With a late kick and a lunge, Caster Semenya ensured an automatic qualifying spot in the next round of the 800 meters when she finished third in her opening heat at the world championships on Wednesday.

The 2009 world champion and 2012 Olympic silver medalist was running in seventh place rounding into the last straight and surged to finish in 1 minute, 59.59 seconds, just behind Marina Arzamosova of Belarus and Linsey Sharp of Britain in the fastest of the six heats.

Defending champion Eunice Sum of Kenya also qualified automatically, winning her heat in 1:59.67.

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10:20 a.m.

Mo Farah stumbled a couple of times on the track Wednesday as he started the second stage of his bid for a long-distance double at the world championships.

Farah, who won the 5,000- and 10,000-meter gold medals at the 2012 London Olympics and has already won the 10,000 title in Beijing, stumbled halfway through his opening heat of the 5,000 and again tripped in a tight pack about 150 meters from the finish. He recovered his footing quickly to cross in second place in his heat to advance in 13 minutes, 19.44 seconds.

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9:40 a.m.

Usain Bolt will be back in action in the semifinals of the 200 meters on Day 5 of the world championships, which got underway with the first round of the 5,000 meters and qualification in the women's hammer throw.

Triple jump for the men and the women's 800 will follow in a morning session that concludes with the first round in the 110-meter hurdles.

There are five finals on the program Wednesday, with the men's javelin and the 400 and women's pole vault, 400-meter hurdles and steeplechase.