London (CNN) -- China claimed the first Olympic gold of the London 2012 Games Saturday, with a victory for 23-year-old Siling Yi in the women's 10-meter air rifle shooting.
Meanwhile, rival American swimmers Michael Phelps and Ryan Lochte are set to go head-to-head in a battle that will be a highlight of the first official day of the Games.
And 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 on Monday for the steroid stanozolol, the International Olympic Committee said, and has been excluded from the competition.
Queen Elizabeth II, who officially declared the Games open late Friday, made an appearance at the Aquatics Center Saturday to watch the action.
Phelps and Lochte are competing in the men's 400-meter individual medley -- a race that combines four different swimming strokes -- after both made it through the heats to the final, Phelps only by a whisker.
The 27-year-old Phelps, who already has 14 gold medals from previous Games, is looking to add to his pot of Olympic gold.
Lochte, thought of as the biggest threat to Phelps, is hoping to live up to the hype.
The highly anticipated match-up has had many choosing sides.
Presumptive GOP presidential candidate Mitt Romney said he was leaning towards Phelps.
"I think it's more likely to be Phelps but I don't know," Romney said Friday during the opening ceremony.
Legendary swimmer Mark Spitz, winner of seven medals at the 1972 Olympics, said he thinks Phelps' experience will help him in the grueling 400-meter individual medley.
"I put my money on Michael," Spitz said. "It's going to be a good race. Any time they are swimming together it is going to be a great rivalry. A great competition."
But the Phelps-Lochte race is not the only highly anticipated swimming showdown Saturday.
The hosts will get to cheer for their own when Hannah Miley competes in the women's 400-meter individual medley. Miley, who has been called one of Britain's best swimmers, could be challenged by American Elizabeth Beisel and Hungarian Katinka Hosszu.
Team USA's Dana Vollmer set a new Games best of 56.25 seconds in the heats of the women's 100-meter butterfly.
Britain's hopes are high for a medal in Saturday's 250-kilometer cycling road race, in which newly-crowned Tour de France champion Bradley Wiggins is expected to aid fellow Briton Mark Cavendish's quest for Olympic gold.
Rowing, another sport in which Britain hopes to excel, also got under way Saturday morning on the lake in Eton Dorney, to the west of London.
Women's basketball begins
Beijing bronze medal winner Russia squared off against Canada Saturday as women's basketball got under way. Later in the day, Team USA plays Croatia.
All teams may be trying to keep the U.S. women from winning their fourth straight gold medal. In fact, at the Beijing Olympics in 2008, the 2004 Games in Athens and in Sydney in 2000, the gold medal match-up pitted Australia versus the United States.
Australia, led by 6-foot-5 Lauren Jackson, starts play late Saturday against Team GB.
Women footballers get the ball, men take a break
Women's football comes to the fore Saturday as the men take a break, with Team GB taking on Cameroon fresh from the host nation's rousing 1-0 victory over New Zealand.
Some 25,000 fans showed up to Wednesday's match against New Zealand, the biggest attendance for a women's international match in Britain.
Current FIFA Women's World Cup holder Japan kicked off against Sweden Saturday, with both teams coming off Wednesday victories. Team USA plays Colombia, after surviving a scare against France Wednesday.
source: CNN
