The Olympic torch began its final journey to the opening ceremony of the Games today beneath the outstretched arms of Rio de Janeiro's iconic Christ the Redeemer statue, while anti-government protests clogged the famous Copacabana beach boulevard.

After seven years of preparations for today's opening at the Maracana stadium, organisers hope the start of the Games will turn the page on months of bad publicity for Rio, from polluted water to faulty plumbing at the athletes' village and worries about the Zika virus.

Under cloudless blue skies, former Brazilian women's volleyball player, Maria Isabel Barroso Salgado, lifted the flame beneath the giant statue of Christ that overlooks downturn Rio and the waters of Guanabara Bay.

"May this be the moment for us to overcome difficult times and to work as a team, to make our country and our world fairer and safer," said Archbishop Orani Joao Tempesta, flanked by Rio Mayor Eduardo Paes.

Having won the Olympics in 2009 during an economic boom, Brazil since slipped into its worst recession in decades and a political crisis that has deeply divided the nation of 200 million people.

The torch's three-month, 20,000-km journey across Brazil ran into difficulties this week as protests flared in towns around Rio against the Games' $12 billion price tag, at a time of high unemployment, rising crime and cutbacks to health and education spending.

A protester at Copacabana beach. Photo: Reuters

Thousands of flag-waving protesters blocked traffic on the curving boulevard beside Copacabana beach, in front of the city's storied Palace hotel, calling for the removal of centre-right interim President Michel Temer.

After taking office when leftist President Dilma Rousseff was put on trial in the Senate for breaking budget rules, Temer has taken Latin America's largest economy - and one of the world's most unequal countries - to the right.

"We want to show the world that we won't stand for this totally illegitimate president," said sociologist Luiz Mazzei, who arrived with his wife wearing "Temer Out" shirts.

"It's a shame. We're so excited for the Olympics. We bought tickets for almost every day. But now it's an awkward mix: we're happy about the Olympics but fed up with Brazil's situation."

SECURITY TEST

Rio will seek to put that behind it tonight when fireworks light up the night sky above the Maracana. Some 50,000 spectators are expected, with some 3 billion people tuning in around the world as Brazil lifts the curtain on its second major sporting event in two years, after the 2014 soccer World Cup.

Security challenges in the sprawling beachside city are at the forefront of many people's minds, not only because of Rio's reputation for violent crime but also due to a spate of deadly attacks in Europe and the United States.

Last month, Brazil detained 12 people under tough new anti-terrorism laws on suspicion of links to Islamic State last month but insists the threat to the Games is 'minimal'.

With many of the Games' 11,000 athletes and dozens of heads of state in attendance, the opening ceremony will be the first major test of Rio's preparedness. In the latest of a series of crime incidents in the run up to the Games, police arrested a Moroccan Olympic boxer on sexual assault charges.

With more anti-government protests scheduled for today, police cleared the area around the stadium.

Brazil has deployed some 85,000 police and troops, roughly twice the number at London's 2012 Olympics, to protect locals and the half million tourists expected to visit the city.

Protesters are calling for interim president Michel Temer to step aside. Photo: Reuters

Rio has consistently pulled off massive events with few security hiccups, including Carnival, the 2014 World Cup final and one of the world's biggest New Year's Eve bashes.

In what organizers have called a low-tech ceremony constrained by the dire economy, Brazil will showcase its natural treasures and the cultural riches created by one of the world's most diverse nations.

Samba, Carnival and the famously fun Brazilian spirit are expected to play heavily into the three-hour ceremony, as will a call to save the planet from climate change.

One of the most anticipated moments will be seeing which famous Brazilian will light the Olympic cauldron. In a surprise announcement, representatives for soccer legend Pele said he would not be taking part.