Swimmer Michael Phelps demolished his own world record to win a first Olympics gold on Sunday in the quest for an unprecedented eight, but conflict in Georgia and a dozen bomb attacks in west China spoiled the party mood.
Listening to hip-hop on headphones as he walked to the block, Phelps went on to win the 400 metres individual medley at China's futuristic and full-to-capacity Water Cube. His time was 1.41 seconds quicker than a previous best he set just six weeks ago.
On a thrilling day in the pool, Phelps raised his arms to savour triumph in what he calls his weakest event.
He was watched by President George W Bush and cheered by flag-waving compatriots and thousands of Chinese.
"I'm pretty happy with that ... it was all adrenaline," said Phelps, calling a thumbs-up by Bush in the stands "pretty cool".
"I tried to find my mom but I couldn't find her."
Even if Phelps wins only half his eight race competitions, he will hold more Olympic gold medals than any other athlete.
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But the 23-year-old looks in great shape to try and match his own six golds at Athens 2004 then maybe go one further than Mark Spitz's 1972 record of seven wins at one Games.
Despite the Phelps phenomenon, the Games' mood on Day Two was marred by attacks by suspected Muslim separatists in Xinjiang, some 3,000 km from Beijing. Seven of the attackers died, and a security guard was also killed.
An attack killed 16 police in the same region a week ago.
Beijing says it has foiled past plots by militants in Xinjiang to sabotage the Olympics. Critics accuse China of exaggerating the threat to justify repression.
Chinese authorities hope the Games will finally put the spotlight on sports after a build-up dominated by accusations of rights abuses and concerns over pollution despite Beijing's desire to showcase its modern face and economic might.
On the first day, though, a Chinese man stabbed to death the father-in-law of a U.S. men's volleyball coach at a tourist spot, then leapt to his death at the ancient Drum Tower. Organisers said the attack was a one-off and Beijing was still safe.
GEORGIAN, RUSSIAN SHOOTERS EMBRACE
Beyond China too, distant crises spoiled the Games' truce.
Georgia's team offered to leave over the conflict with Russia in South Ossetia. But President Mikheil Saakashvili sent instructions to stay "in the best interests of the country".
Georgian shooter Nino Salukvadze hugged Russian rival Natalia Paderina after they took bronze and silver respectively in the 10-metre air pistol. "If the world were to draw any lessons from what I did there would never be any wars," Salukvadze said.
"There should be no hatred among athletes and people."
After Phelps left the Water Cube public agog, Australia's Stephanie Rice followed suit to smash the world record and win the same 400 metres individual medley event for women.
Park Tae-hwan won the men's 400 freestyle to give South Korea a second gold, while Zhang Lin became the first Chinese man to win an Olympic swimming medal with his silver.
Dara Torres, a 41-year-old mother, became the oldest athlete to win an Olympic swimming medal, helping the Americans to relay silver. "The water doesn't really know what age you are," she said.
China came second in the medals table in Athens and aspires to outstrip the United States this time. As expected, given their strength in the first sports, China had taken an early lead with four golds by mid-afternoon Sunday.
Guo Wenjun gave the hosts one gold with her pistol, while China's synchronised 3-metre springboard pair won the other.
In gymnastics, China's women beat an injury-hit U.S. team in qualifiers despite He Kexin's crash off the asymmetric bars.
Chinese fans are also focused on Sunday's basketball blockbuster between the hosts, led by 7ft 6in Yao Ming, and a star-studded United States smarting from bronze in Athens 2004.
It may be the most-seen sporting contest in China's history.
Recalling the high-profile doping cases of Athens, the International Olympic Committee ruled Greek sprinter Katerina Thanou could not compete in Beijing despite completing a ban.
In what the IOC called a "scandalous saga", Thanou and fellow runner Costas Kenteris missed a drugs test on the eve of the Athens Games, overshadowing the opening.
Bush went to church then met Chinese President Hu Jintao for private talks of the sort he says include frank discussions on human rights. "I enjoy our conversations," Bush said.
Hu thanked Bush for his fourth trip to China, the most by a sitting U.S. president. "This is a true testament to the importance you place on relations with China," he said.
Rain cleansed Beijing's smog-filled air on Sunday, but some athletes were still taking precautions.
"Me being healthy is the most vital thing about me being here to compete," U.S. hurdler Terrence Trammell said, swapping a paint mask he brought from home for one given by Chinese medics.
