Rio 2016 Olympics - Security has emerged as a top concern at the 2016 Olympics after a string of killings, kidnappings and robberies in Rio de Janeiro in recent days.
Queues snaked up to 2km long outside some venues as spectators waited for security checks while competition went on inside.
Gymnasts performed in front of rows of empty seats in an arena that can take 13,500 people.
At the tennis centre, where former world number one Ana Ivanovic played in front of virtually empty stands in the first round, fans had to wait more than 20 minutes to buy water.
Spectators encountered similar situations at the rowing and the rugby venues as temperatures hit 32°C.
Organisers blamed a lack of coordination among security personnel, including the police, Games staff and private security firms, and they have promised an immediate improvement.
Earlier a loud blast erupted near the cycling race's finish line and a stray bullet ripped through the media tent at the equestrian venue, missing a New Zealand press attache by metres.
In a statement the New Zealand Olympic Committee said: "A bullet entered the press conference work room at the Equestrian Venue at Deodoro in Rio and landed on the floor".
Onlookers were shocked when the bullet pierced the tent, leaving visible holes in the fabric roof and wall.
Security has since been stepped up in venues and at the Olympic Village.
New Zealand chef de mission Rob Waddell said the incident was being taken very seriously.
He understood from the police liaison team travelling with the New Zealanders that the bullet was unintentionally discharged.
Waddell said it went over the press attache's head by about five metres.
"We understand she's okay, fortunately we had NZOC (Olympic Committee) staff with her at the time and they immediately went and sat in a building with a concrete structure to remain safe."
Waddell said the woman was being offered ongoing support. He said the incident was being investigated and officials were liaising with the appropriate authorities.
The Brazilian military carried out a controlled explosion near the Copacabana finish line of the men's road cycling race on Saturday, witnesses said.
Military bomb disposal experts were at the scene and the police kept crowds away.
The explosion stunned crowds gathering for the end of the race. The race leaders were about 100km away at the time.
Day One unsettling
It made for an unsettling day one of the Rio Games, which were launched in a blaze of colour by a flamboyant opening ceremony.
But in further violence, 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.
At the 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 game.
"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.
"We do hope nobody missed any important part of a competition for being on lines."
The events overshadowed a busy opening day of action in which little-known American teenager Virginia Thrasher became the first gold medallist in the first of 306 medal events.
Thrasher, 19, fired the first shot for the United States when she shocked China's Du Li and Yi Siling to win the women's 10m air rifle.
"This is beyond my wildest dreams," beamed the West Virginia University engineering student, who clinched victory on her final shot.