The first full day of Olympic competition saw three new swimming world records fall, Vietnam's first-ever gold medal, and long lines for spectators as organizers struggled with security glitches.
Much of the opening day's best action at the 2016 Summer Olympic Games in Rio de Janeiro was in the swimming pool. Australia set a world record in the women's 4x100 meter freestyle relay, with sisters Bronte and Cate Campbell helping the team defend its 2012 Olympic gold while breaking its own 2014 record with a time of three minutes and 30.65 seconds.
Hungary's Katinka Hosszu won gold in the women's 400-meter individual medley swimming competition with a world-record time of four minutes and 26.36 seconds, shattering the previous record by more than two seconds.
And Britain's Adam Peaty, competing in the Olympics for the first time, set a new world record of 57.55 seconds in the men's 100-meter breaststroke heats.
Vietnam rejoiced after 41-year-old Hoang Xuan Vinh took the men's 10-meter air-pistol competition, ending the country's six-decade-long wait for a gold medal. The army colonel, who first learned to shoot with an AK-47 assault rifle, won with a near-perfect final shot.
On the basketball court, the heavily favored U.S. men's team opened with a 119-62 thrashing of China, the biggest margin of victory in Olympic competition since 1996. In women's tennis, American Venus Williams lost in the first round for the first time in a record five Olympic singles appearances, losing 4-6, 6-3, 7-6 (5) to Belgium's Kirsten Flipkens.
Long Lines, Empty Stands
The day featured a number of lowlights in ann out of the arena.
Fans were horrified when French gymnast Samir Ait Said made an awkward landing from a vault and broke his left leg. German gymnast Andreas Toba also withdrew from the games after tearing a ligament in his right knee.
And organizers apologized on August 6 for keeping fans waiting in long lines at security checkpoints while they were trying to enter event venues. At some events, athletes competed in front of nearly empty grandstands while outside lines stretched for many blocks with temperatures above 30 degrees Celsius.
"We apologize for everybody standing outside the venues," games spokesman Mario Andrada said. "Within the next hours we will be in much better shape."
A pair of incidents highlighted concerns expressed ahead of the games about security.
A bomb squad carried out a controlled detonation of an unattended bag near the finishing line of the men's road cycling race. The competitors were some 70 kilometers away at the time, however, and the race was not affected.
A stray bullet hit the press center at the Olympic equestrian venue. According to one report, the bullet narrowly missed an official with the New Zealand team. Olympic authorities gave assurances that it was a stray bullet, and that the venue was not a target.
Host Brazil got its first medal when Felipe Wu took the silver in the men's 10-meter air gun event. Virginia Thrasher, a 19-year-old from the United States, took the first gold medal of the games in the women's 10-meter air rifle competition.
Judoka Beslan Mudranov took the gold in the men's 60-kilogram judo competition, scoring the first medal for Russia's beleaguered Olympic team. More than 100 Russian athletes were barred from competing amid strong allegations of widespread, state-organized doping.
"I am very pleased that I have won the first gold medal," Mudranov was quoted as saying. "Everybody knows what the situation was. I am sure that this gold medal is not the last."
Kazakhstan's Yeldos Smetov took the silver medal in the same event, and Uzbekistan's Diyorbek Urozboev took the bronze. Kazhakstan's Otgontsetseg Galbadrakh took the bronze in the women's 48-kilogram judo competition.
The second day of competition will feature a familiar face -- Uzbekistan's Oksana Chusovitina. The qualification round for women's gymnastics will see the 41-year-old gymnast compete in her seventh Olympic games, with the vault seen as her best chance for a medal.
In tennis, No. 1 seeds Novak Djokovic and Serena Williams will take the court. And in volleyball, Iran's men's team will make its Olympic debut amid questions about whether Iranian women will be in attendance. Volleyball is a popular sport in Iran, but female fans are denied the opportunity to attend matches in Iran by the authorities.
During the opening ceremonies, Iranian archer Zahra Nemati -- who will be competing both in the Olympics and Paralympics -- served as the country's first female flagbearer.
With reporting by Reuters, AP, TASS, and dpa