British swimmer Adam Peaty broke his own world record as he reached the 100m breaststroke final but there were no GB medals on day one of the Rio Olympics.
After a new best in the heats, Peaty qualified for Monday’s final (02:53 BST) in the second-fastest time ever.
GB cyclists Chris Froome and Geraint Thomas both missed out on medals in a dramatic men’s road race.
But British cyclist Lizzie Armitstead can make amends when she goes in the women’s event on day two at 16:15 BST.
She was only cleared to compete 15 days before the Games began after appealing against a ban for missed drugs tests.
American shooter Ginny Thrasher, 19, won the first gold of the Games, while two swimming golds helped Australia top the medal table.
There was drama elsewhere with a stray military bullet landing in a media tent and police carrying out a controlled explosion on an unattended bag near the finish line of the men’s cycling road race on Copacabana’s sweeping boulevard.
Peaty favourite for swimming gold
Peaty – the swimmer who was once frightened of water – scared his rivals with two blistering swims which make him firm favourite for the gold medal.
The 21-year-old City of Derby swimmer clocked 57.55 seconds to break his own world record of 57.98, then swam 57.62 to win his semi-final.
He is bidding to become the first British man to win Olympic gold in the pool since Adrian Moorhouse 28 years ago.
Hannah Miley narrowly missed claiming Britain’s first medal of the Games, finishing fourth in the women’s 400m individual medley.
Hungary’s Katinka Hosszu took the gold with a new world record time of four minutes 23.34 seconds, over two seconds faster than the previous mark.
Max Litchfield was also fourth, in the men’s 400m individual medley, while James Guy led at halfway in the 400m freestyle final, before fading to finish sixth as Australian Mack Horton claimed gold.
Big winners on opening day
A gruelling road race ended with Belgian Greg van Avermaet sprinting first across the line after passing Poland’s Rafal Majka in the last few seconds.
British hopes ended when Thomas crashed on the final descent, after Froome and Adam Yates failed to stay with the leaders in the 237.5km race.
Welshman Thomas remounted to finish 10th, one place ahead of Froome, who had to be told to register for the race by two BBC journalists after failing to hear his name being called over the public address system.
Earlier, the first gold medal of the Games went to teenager Thrasher.
A biomedical engineering student, she secured her maiden major international victory in the women’s 10-metre air rifle, scoring 208.0 to leave China’s 2006 world champion Du Li with silver.
A day of firsts
- First athlete to represent the refugee team – A year since fleeing Syria and being forced to swim for her life, Yusra Mardini, 18, won her women’s 100m butterfly heat, but her time was not quick enough to progress.
- First Olympic gold medal for Vietnam – Hoang Xuan Vinh beat hometown favourite Felipe Almeida Wu on the final shot of the men’s 10-metre air pistol competition.
- Games debut for rugby sevens – Great Britain’s women beat Brazil 29-3 and Japan 40-0 in the group stages.
- Italy’s Carmine Tommasone made history – the first professional to step into an Olympic boxing ring beat Mexican lightweight Lindolfo Delgado on a unanimous points decision.
From coma to leader: British highlights
Rider William Fox-Pitt is eyeing an extraordinary equestrian success as he leads the eventing competition at the halfway point of the dressage, the first of three disciplines.
“I’m lucky to be here,” said the 47-year-old, who was in a coma 10 months ago after a fall.
Britain scored a notable victory in the women’s hockey, beating Australia 2-1 in their opening group match, although the men were defeated 4-1 by Belgium.
Rowers Katherine Grainger and Vicky Thornley went through to the semi-finals of the women’s doubles sculls, while the men’s lightweight four and men’s pair also progressed.
Gymnasts Max Whitlock and Louis Smith limbered up for a potential gold medal showdown on the pommel by leading Britain into the final of the men’s team event, but Commonwealth judo champion Ashley McKenzie was in tears after being knocked out of the -60kg category.
Explosion, a stray bullet, and long queues
Brazil’s bomb squad carried out a controlled explosion on an unattended backpack near the cycling road race finish.
The bag may have belonged to a homeless man, a spokeswoman for the public security department said.
A loud blast shook the media seats near the finishing line amid tight security at South America’s first Olympics.
Meanwhile, there was a scare at the Olympic Equestrian Centre – which is located near a military compound – as a bullet pierced the roof of the media tent and landed on the floor. The competition was not disrupted and nobody was hurt.
Rio 2016 organisers have apologised after spectators faced long queues to enter the Olympic Park and said they have increased security staff at checkpoints.
Analysis – Tom Fordyce, BBC chief sports writer
“On a day when a little too much went a little too wrong for the Rio organisers – long queues, small crowds, a stray bullet and a controlled explosion – the start of competition and quality of performances has helped balance out some of those worries.
“For Britain, the displays of Adam Peaty promise a rich dividend on day two, while the unexpected success stories so important to an Olympics have got people talking about sport rather than scandal.
“Few Olympics escape their first few days without teething problems. At this point four years ago, all the talk in London was of how the army had been brought in to bail out the struggling security system. Rio will look to improve – fill more seats, speed up journeys, bring more noise – as the weekend continues.”
Agony on opening day
French gymnast Samir Ait Said suffered a broken leg while performing in the vault in the men’s qualification event.
Said writhed on the ground in agony while medical officials tended to him and he was carried away on a stretcher to a standing ovation.
Serbian pair Milos Vasic and Nenad Bedik capsized during qualification for the men’s pair rowing semi-final at Lagoa Stadium.
Former Olympic tennis champion Venus Williams was eliminated in the first round, as Belgian underdog Kirsten Flipkens fought back for a 2-6 6-1 6-2 win.
Meanwhile, Brazilians will have to wait a bit longer for their country to earn its first gold medal at their home Olympics after defending champion Sarah Menezes suffered a shock defeat in the judo -48kg quarter-finals.
Athletes fail drugs tests
Cypriot weightlifter Antonis Martasidis joined an unnamed Greek competitor as the first two athletes sent home from Rio 2016 for doping.
Russian swimmer Yulia Efimova has been been cleared to compete in Rio after a convoluted drugs case that saw her go through the Court of Arbitration for Sport.
The world champion will line up in the 100m breaststroke heats on Sunday after initially being banned because of a previous doping violation.
Russia claimed their first gold as Beslan Mudranov triumphed in the men’s -60kg judo final.
He is among a team of more than 270 Russian athletes at the Games, about two-thirds of the original entry despite the World Anti-Doping Agency (Wada) recommending a blanket ban after a state-sponsored doping scandal.
Long and the short of Rio 2016
Competitors have been getting into the Olympic spirit, taking selfies and sharing photos with athletes from other sports on social media.
Here, from Instagram, is Team USA basketball player Deandre Jordan (6ft 11in) with gymnast Ragan Smith (4ft 6in).
What to look out for on day two
Armitstead won Britain’s first medal of the 2012 Games when she claimed silver and will aim to go one better after a difficult build-up.
The women’s road race is expected to finish at about 20:00.
Britain’s defending tennis champion Andy Murray begins his campaign as he looks to add another tennis gold to his second Wimbledon title.
The tennis action starts at 14:45 BST, with Murray due third on Centre Court against Serbia’s Victor Troicki, while Johanna Konta is fourth on court three against Stephanie Vogt of Liechtenstein.
- Badgers may not spread TB to cattle through direct contact
- Nasa-style mission needed to map ocean floor
- North Korea conducted 'very important test' at satellite launch facility: state media
- Police kill 20 suspected sandalwood smugglers during gun battle in southern India
- Rights activists laud pardon for Salvadoran woman imprisoned after apparent miscarriage
- 9 Twitter Best Practices for Business