The Rio Olympics got off to a troubled start today as a loud blast erupted near the cycling race's finish line and a bullet ripped through the media tent at the equestrian venue.
Long queues also formed outside venues -- as competition went on inside -- as volunteers and security staff struggled to cope with a sudden influx of fans.
Brazilian military carried out a controlled explosion near the Copacabana finish line of Rio Olympics men's road cycling race today, witnesses said.
Military bomb disposal experts were at the scene of the explosion and kept crowds away with police.
The explosion stunned crowds gathering for the end of the race. The race leaders were about 100 kilometers (60 miles) away at the time.
Elsewhere at the Deodoro venue, onlookers were shocked when a bullet pierced the temporary venue housing media, leaving visible holes in the fabric roof and wall.
It made for an unsettling day one of the Rio Games, which were launched in a blaze of colour by yesterday's flamboyant opening ceremony.
But in further violence yesterday, police gunned down a mugger outside the ceremony venue, the Maracana stadium, and a woman was shot and killed by armed assailants near the Olympic Boulevard.
The events overshadowed a busy opening day of action in which little-known American teenager Virginia Thrasher became the first gold-medallist, in the women's 10m air rifle, the first of 306 medal events.
In swimming, China's Sun Yang will defend his 400m crown later today, and Britain's Tour de France Chris Froome was among the road race competitors.
Serbian rowers Milos Vasic and Nenad Bedik capsized in choppy waters at the Rodrigo de Freitas lagoon, while Iran's Ghader Mizbani suffered a terrifying crash in the cycling race.
At Olympic Park, the Games' hub, fans complained bitterly over transport and logistical problems which soured their experience on a sweltering day in Rio.
"We were caught like sardines in the bus and there are huge queues here," said Adriana Barbosa who travelled to Rio de Janeiro from Sao Paulo for the weekend.
Rio Olympics spokesman Mario Andrada apologised for the long queues and admitted the tournament needed to raise its "Indeed we have problems on some venues especially in the Olympic Park," he said. "We apologise to everybody who is standing under the sun and in lines outside of venues.
