Czech Republic's Zuzana Hejnova became the first woman to successfully defend her 400 metres hurdles title after 14 editions of the world championships when she won gold at the Bird's Nest Stadium.

She produced a dominating and controlled performance to come home two metres clear of Shamier Little, the United States champion, in a world leading 53.50 seconds.

Little, the 20-year-old US collegiate champion, took silver on her worlds debut in 53.94, with her team-mate Cassandra Tate winning bronze with 54.02.

The threat from Jamaica's Kaliese Spencer vanished at the second hurdle, where the Commonwealth champion blundered and lost all momentum and was never able to get back into the race, trailing home last of the eight finalists.

The 28-year-old Hejnova, drawn in lane five, was clearly in the lead by the time of the seventh flight and held a three-metre advantage into the home straight which was never seriously challenged.

"It was a very hard final for me because I was the defending champion," Hejnova said. "It got very tough at the end."

Meanwhile, Wayde van Niekerk ran the fastest 400 metres since 2007 to become the first South African to win a world championship sprint title.

The 23-year-old went hard from the start and held off reigning champion La Shawn Merritt of the United States down the home straight to claim the title in 43.48 seconds.

A personal best of 43.65 was worth no better than silver for Merritt, who stayed on the South African's shoulder around the final bend but could not find enough gas in the last 50 metres to overhaul him.

Olympic champion Kirani James of Grenada finished third to claim bronze in 43.78, his best run of the year.

Van Niekerk was taken away from trackside on a stretcher, denying the 23-year-old a deserved victory lap at the end of an exhausting run which saw him become the fourth fastest man ever over 400m.

Cuba's Yarisley Silva needed a jump of 4.90 metres to win a thrilling women's pole vault contest and claim her first major global title.

Pushed all the way by Brazil's Fabiana Murer and Greece's Nikoleta Kyriakopoulou, the London Olympic silver medallist won gold with her third attempt at the winning height before failing three times at 5.01m.

Silva needed all three goes to get over at 4.70 and join an unprecedented seven women going for 4.80.

Murer and Silva cleared 4.85 at the first attempt to ultimately leave Kyriakopoulou with bronze.

With the noisy crowd roaring her on, Silva slid over the bar at 4.90 to win the title. Murer's clearance at 4.85 was a South American record and she took silver.   

Hyvin Jepkemoi continued Kenya's monopoly of the 3,000m steeplechase when she proved to be tougher than all her rivals in a hard-fought final lap to win the world title.

Jepkemoi, 23, produced a sub-66 seconds last 400 and had to battle off the final barrier against the favourite, Tunisia's Habiba Ghribi, and Germany's Gesa Krause, to take Kenya's sixth gold of the Beijing championships in 9.19.11.

Ghribi, the runner-up at the 2012 London Olympics and 2011 world championships, had to settle for silver once more as the Kenyan passed on her outside.

Grhibi clocked 9.19.24, to Krause's bronze-winning 9.19.25, a personal best.

The first half of the race was slow, with only a front-running effort by Lalita Babar of India picking up the pace towards the final kilometre.

Into the final 600m, American Emma Coburn made a bid for glory but, as the bell for the final lap rang, Ghribi took up the running towards a title which many had thought was a foregone conclusion.

However, as the Tunisian took the final water barrier in conventional style, with one foot on the barrier, Jepkemoi hurdled the obstacle and forced herself past her rival.

As Coburn faded over the final half-lap, eventually placing fifth, the three medallists came off the final fence in line but it was Jepkemoi, sixth in the world final in Moscow two years ago, who was the strongest finisher this time.

Earlier, Julius Yego had shown Kenyan dominance extends further than the track by claiming the country's first world title in a field event when winning the men's javelin final.

Yego's winning 92.72m throw comes a day after Nicholas Batt won the 400m hurdles title, the shortest distance over which any Kenyan has become a world champion.

In an event which has long been a European stranglehold, there was a one-two for Africa, as Egypt's Ihab El Sayed took the silver medal with his 88.99m second-round effort.

Finland's Tero Pitkamaki maintained European pride by taking bronze with his 87.64m best effort. Thomas Rohler, of Germany placed fourth with 87.41, after having led in the early stages.

Yego, 26, is diminutive by the standards of international javelin throwers, standing only 1.75m tall.

Rejected as a runner by sports coaches as a schoolboy, he taught himself the javelin by watching videos on YouTube.

After the first two rounds in the Bird's Nest Stadium, Yego, winner of Commonwealth Games gold last year, was trailing Rohler and El Sayed.

For the third round, Yego threw himself diving to the ground at the end of his run-up, and his spear hung in the stormy Beijing evening sky before landing just eight cm short of the championship record, set in 2001 by the world record-holder, Jan Zelezny.

Yego's throw is the longest anywhere since then, and his mark betters a Commonwealth record which was held by Briton Steve Backley since 1992.