"It is great to win such a big competition, my second gold."
PIC: David Rudisha says he had no doubts he would win again. (AFP)
Kenya's David Rudisha claimed a majestic Olympic double in the 800m as an unknown Brazilian pole vaulter scored a shock gold medal on a night of upsets.
Rudisha became the first man in 52 years to clinch back-to-back 800m titles after producing a phenomenal last lap kick to win in 1min 42.15.
"Running 1:42, it's just fantastic. I had no doubts before," said Rudisha.
"It is great to win such a big competition, my second gold," he said. "It's so great. I am so excited. It is the greatest moment of my career."
The last man to win consecutive 800m titles was New Zealand's Peter Snell in 1960 and 1964.
Algeria's reigning Olympic 1500m champion Taoufik Makhloufi took silver in 1:42.61, with American Clayton Murphy claiming bronze in 1:42.93.
But Rudisha's imperious performance was a rare example of form holding sway as upsets dominated on an evening of pulsating drama.
The biggest shock was scored by unheralded Brazilian Thiago Braz in the pole vault who conjured the performance of his life to dethrone France's defending Olympic champion Renaud Lavillenie and spark bedlam amongst the fiercely partisan Rio crowd.
As a thrilling duel reached its climax, Lavillenie was visibly upset by the crowd's relentless booing as he prepared for his run-up, at one point wagging his figure in disgust at the catcalls.
Braz, who had not even managed to qualify for the final at the World Championships in Beijing last year, cleared 6.03 metres to set a new Olympic record.
World record holder Lavillenie then pitched everything on a last gasp vault at 6.08m but failed to leave 22-year-old home hero Braz celebrating a famous win.
American Sam Hendricks took bronze with a vault of 5.85.
"I am very happy. We worked really hard for this moment -- not for the gold but to take a medal. For Brazil, it is amazing. I try to do my best for the people, they believe in us," Braz said.
But Lavillenie could not hide his disgust at the crowd's conduct.
"There is no respect, no fairplay. It's the Olympics, if there's no respect in the Olympics, where can we get respect?" the Frenchman said.
"I'm very, very sad and disappointed by the Brazilian public that was in the stadium."
Miller dive stuns Felix
Another stunning upset marked the conclusion of the women's 400m, where world champion Allyson Felix was beaten by a spectacular head-first dive for the line by Shaunae Miller of the Bahamas.
Miller hurled herself across the line to win in 49.44sec with 2012 Olympic 200m champion Felix taking silver in 49.51.
Shericka Jackson of Jamaica claimed bronze in 49.85.
Miller had got off to a flying start, burning through the first 300 metres to build a big lead heading into the home stretch.
But the experienced Felix looked to have timed her race to perfection, gradually reeling in Miller over the closing metres as the line loomed.
Miller's all-or-nothing lunge however was good enough for gold.
"This is the moment I have been waiting for, I just gave it my all," Miller said.
"I am just so happy, so grateful, such emotions I just can't say. I've been going through so much this year. Everyone at home will all be celebrating right now."
The defeat left Felix, the most decorated female track and field athlete in history with 20 Olympic and world championship medals to her name, distraught.
Speaking to reporters after the race she choked back tears as she digested a shattering loss.
"I'm disappointed. It's been a tough year and I was kind of hoping it would come together," she said.
"I didn't think about lunging myself. I tried to give it all I have but I didn't have any more to give in the last 10 metres."
Earlier the action in the stadium had been halted after torrential rain lashed the arena, forcing officials to rerun two heats of the 110m hurdles.