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London (CNN) -- Ryan Lochte captured the United States' first gold medal of the 2012 Olympic Games on Saturday, soundly defeating rival swimming great Michael Phelps in a highly anticipated men's 400-meter individual medley, while China blazed past its rivals throughout the day to secure a Games-best four gold medals.
Brazil's Thiago Pereira secured silver in the individual medley, while Phelps did not medal, coming in fourth place. Japan's Kosuke Hagina won bronze.
"I put the work in," Lochte said Saturday after the race. "I'm just going out there and having fun, and doing what I do best."
Both men had made it through qualifying heats to the final -- Phelps only by a whisker.
His subpar performance put the former champion in lane 8 rather than in the preferred middle lanes, where there's less chance of disruption from other swimmers' waves.
Lochte was in lane 3.
The 27-year-old Phelps, who already has 14 gold medals from previous Games, had been looking to add to his pot of Olympic gold, and will get another shot when he likely faces Lochte in the 200-meter individual medley, as well as the 200-meter and 100-meter butterfly.
But the Games' attention quickly shifted on Saturday to Lochte's dominating performance.
"I know it's my time and I'm ready," he said after his win.
History was made soon after the race, when China's Sun Yang won the men's 400-meter freestyle, becoming the first Chinese man ever to win an Olympic gold medal in swimming.
China's Ye Shiwen made history of her own by breaking the world record in the women's swimming 400-meter individual medley, with a time of 4:28:43. American Elizabeth Beisel took the silver medal in the medley.
The Games' host faced disappointment when it failed to pick up a single medal on Saturday, particularly when Hannah Miley, considered one of Britain's best swimmers, finished fifth in the event.
"Apologies if anyone had high expectations of me," said Miley. "I gave it absolutely everything I had."
Earlier Saturday, China claimed the first Olympic gold of the games with a victory for 23-year-old Siling Yi in the women's 10-meter air rifle shooting.
"I'm very excited and happy," she said, quoted by the official Games website. The world's No. 1, who started shooting at age 13, said there had been "a lot of pressure" on her to perform.
China's veteran weightlifter Wang Mingjuan, 26, also powered her way to gold, besting silver medalist Hiromi Miyake of Japan by lifting a combined total of 205 kilograms.
"The gold is the reward for my 12 years' hard work, my dream came true today," she told Chinese state-run media.
With China on top with four golds by Saturday evening, Italy also made a strong showing by securing two, while the United States, South Korea, Brazil, Russia, Kazakhstan and Australia each took one.
The first American medal of the day was a silver, after the men's archery team narrowly fell to Italy in a riveting finals match that wasn't decided until the final arrow.
Meanwhile, the U.S. women's football team ousted Colombia 3-0, securing themselves a quarterfinal spot.
The U.S. men's gymnastics team also performed well Saturday. It advanced to the team finals, on top of rankings for the qualification round, ahead of Russia and Great Britain. Scores from the qualifying round do not carry into team finals, which will be held on Monday.
Four U.S. men also advanced to the individual event finals. Danell Leyva and John Orozco were first and fourth, respectively, in the qualifying rankings for the all-around.
However, controversy reared its head early, as Albanian weightlifter Hysen Pulaku became the first athlete to be sanctioned for failing an anti-doping test at the London Games.
Pulaku, 20, tested positive Monday for the banned anabolic steroid stanozolol, and has been excluded from the competition.
Queen Elizabeth II made an appearance at the Aquatics Center on Saturday to watch the action, as did First Lady Michelle Obama.
Widely hailed as showcasing an inventive, and sometimes eccentric, ceremony, the show included a short film featuring Daniel Craig, the latest actor to play cinematic British spy James Bond, and the queen herself.
As the first rounds of the tennis tournament began, Swiss star Roger Federer returned to the All-England Club where he won the Wimbledon men's singles title only three weeks ago.
Meanwhile, Britain's hopes in Saturday's 250-kilometer cycling road race, in which newly crowned Tour de France champion Bradley Wiggins sought to aid fellow Briton Mark Cavendish to a medal, were dashed as Kazakhstan's Alexander Vinokourov put in a gutsy sprint to take the gold.
Thousands of spectators had lined the route through the streets of London and along leafy roads in neighboring Surrey to catch a glimpse of the riders racing by. Organizers also predict big crowds on Sunday for the women's cycling road race, as tickets aren't needed to watch the action.
Olympic fans, many dressed up in their national colors, packed outdoor viewing areas in Hyde Park and elsewhere to watch the day's events unfold on a big screen.
The government said in a statement Saturday that plans for the management of crowds, security and transport appeared to be going well so far, including the exit of large crowds from the Olympic Stadium following the late-night opening ceremony.
Concerns had been raised ahead of the Games about the capacity of London's already busy transport network to deal with the hordes of visitors heading to the Olympic Park and other venues.
Security also became an issue ahead of the Games when the private contractor G4S revealed it could not provide as many security guards as required. The British military has stepped in to fill the gap.
Beijing bronze medal winner Russia defeated Canada on Saturday as women's basketball started, while later in the day, Team USA routed Croatia by a score of 81-56.
All teams may be trying to keep the U.S. women from winning their fourth straight gold medal. Team USA has played Australia for gold in each of the past three Olympics. Australia, led by 6-foot-5 Lauren Jackson, starts play late Saturday against Team GB.
Team USA's Dana Vollmer also set a new Games best of 56.25 seconds in the qualifying heats of the women's 100-meter butterfly.
Earlier Saturday, Russia's Arsen Galstyan prevailed over Hiroaki Hiroaka of Japan, pinning the contest favorite to take his first gold medal in the men's 60-kilogram judo competition.
And Australia tallied its first gold medal of the games Saturday with a win in the women's swimming 4x100m freestyle relay. The Netherlands took the silver and the United States won bronze.
CNN's David Ariosto, Stephanie Halasz, Amanda Davies and Laura Smith-Spark contributed to this report.