US swimmer Michael Phelps carved his name among Olympic greats on Tuesday, winning a record-equalling ninth career gold on a dominant morning for Americans in the pool.
Only US athlete Carl Lewis, US swimmer Mark Spitz, Finnish distance runner Paavo Nurmi and Soviet gymnast Larysa Latynina have won as many golds as Phelps, who could overtake them all on Wednesday when he swims in two more finals.
"To be tied for the most Olympic golds of all time, with those names in Olympic history ... it is a pretty amazing accomplishment," he said.
Phelps led an American fightback against Chinese dominance of the medal table on day four, but China reclaimed its traditional leadership in men's team gymnastics and won the women's 10 metre synchronised platform diving to keep the competition tight.
The hosts, second to the Americans in 2004, are keen to end the Games in top spot. Sporting triumph would underline the message of new economic and political might that China wants to convey in its no-expense-spared hosting of the Games.
The Chinese have dominated in the weightlifting, winning four of six events, won all three diving golds so far and picked up victories in shooting and judo.
The gymnastics victory was among the sweetest as four years ago the men's team failed to win a medal in Athens. Double world all-round champion Yang Wei led from the front to restore Chinese dominance in front of an ecstatic home crowd.
The victory was "a glory for China", said Yang.
The Chinese team took their inspiration from "Prince of Gymnastics" Li Ning, who lit the cauldron at the opening ceremony on Friday, circling high above the heads of spectators in a daredevil high-wire act.
Little has been left to chance by organisers desperate to make a good impression, with cheerleaders being used to fill vacant seats in several venues.
Some of the opening ceremony fireworks were also "pre-staged" and then rebroadcast to enhance the event's televised choreography, organisers say.
Security was visibly stepped up on Tuesday in the Olympic Green, site of the main venues, with an armoured personnel carrier stationed outside the main press centre and soldiers standing at some of the barriers.
The father-in-law of the American volleyball coach was stabbed to death in Beijing on Saturday, and Chinese authorities say there have also been threats against the Games by Islamist separatist groups active in the far northwest of the country.
Separatists will again be the chief suspects for another attack in the restive northwestern Xinjiang region on Tuesday, the third since the Games began. Three security officers were stabbed to death some 3,000 km (1,900) miles from the capital.
Back in Beijing, Phelps threatens to rewrite many pages of the sporting records in a phenomenal individual display.
His third gold this week keeps him on his long march to a target of eight wins in a single games. That would beat Spitz's 1972 tally of seven golds in one Olympics.
Spitz set world record times in all of his victories at the Munich Games, a feat which Phelps could also eclipse. Each of Phelps' Beijing golds has come in a new world best time.
The lanky 23-year-old American was in imperious form in the 200m freestyle final, leading from the start and pulling a body length clear by the halfway stage. He hit the wall in 1:42:96 to destroy his own world record by 0.90 seconds.
His dazzling swim was the first of three victories for American swimmers in less than 20 minutes, pushing the United States up to second spot in the medal table behind China.
World champion Natalie Coughlin "cried like a baby" on the podium after forcing Zimbabwean Kirsty Coventry to settle for silver in the women's 100 backstroke, her relief all the greater after Coventry had set a world record in the semi-final.
American Aaron Peirsol smashed the world record he set just six weeks ago to retain his Olympic 100 metres backstroke title and maintain his long dominance of the discipline. He starts his defence of his 200 metre title on Wednesday.
Australian world champion Leisel Jones ended eight years of gut-wrenching defeats by winning her first individual Olympic title on Tuesday in the 100 breaststroke.
Criticised for being a sore loser in Athens when she missed out on gold, Jones changed her coach and approach to swimming.
"It has been a long journey, a long eight years," said Jones. "I've gone from a naive 14-year-old to an under-pressure 18-year-old in Athens and now, a relieved 22-year-old."
American swimming success, led by Phelps, has helped draw huge audiences for the Olympics back home, where broadcaster NBC said it had the best ratings for any Summer Games held outside the United States since 1976.
Chen Ruolin and Wang Xin, made it three out of three victories for China in diving, winning the women's synchronised 10m platform. The youthful Chen, just 15, and Wang, who turned 16 on Monday, dived with adult composure to dominate the contest.
China's money market traders are now betting the host country will win 40 to 42 golds in the games, up from 32 in 2004.
(Reporting by Beijing Olympic bureau; Editing by Alex Richardson)