Francis, however, not only looked calm but got even closer to the people. He rolled down his back-seat window, waved to the crowd and touched those who reached inside. He kissed a baby a woman handed to him.
"His secretary was afraid," papal spokesman the Rev Federico Lombardi said. "But the Pope was happy."
After finally making it past crowds and blocked traffic, Francis switched to an open-air vehicle as he toured around the main streets in downtown Rio through mobs of people who screamed wildly as he waved and smiled. He left his popemobile - the bulletproof one - in the Vatican garage so he could better connect with people during the Church's World Youth Day.
The Vatican insisted it had no concern for the Pope's safety as his vehicles eased through the masses, but Lombardi acknowledged that there might have been some "errors" that need correcting.
Many in the crowd looked stunned to see the Pope, with some standing still and others sobbing loudly.
As many as one million young people from around the world are expected in Rio for the Catholic youth fest, a seemingly tailor-made event for the Argentine-born Pope, who has proven enormously popular in his four months on the job. But the fervour of the crowds that regularly greet Francis in St Peter's Square was nothing compared with the raucous welcome in Rio.
Popes generally get a warm welcome in Latin America; even the more aloof Pope Benedict XVI received a hero's welcome when he visited Mexico and Cuba in 2012. John Paul II frequently received rock star treatment, and during one 1996 visit to Venezuela, his motorcade was similarly mobbed when he stopped to greet well-wishers after greeting prisoners.
Outside the Guanabara government palace where the Pope was officially welcomed, Alicia Velazquez, a 55-year-old arts teacher from Buenos Aires, waited to catch a glimpse of the man she knew well when he was archbishop of her hometown.
"It was so amazing when he was selected, we just couldn't believe it. We cried and hugged one another," Velazquez said. "I personally want to see if he's still the same man as simple and humble whom we all knew. I have faith that he's remained the same."
Francis displayed that humility in greeting President Dilma Rousseff.
"So let me knock gently at this door," Francis said in Portuguese at the official welcome ceremony. "I have neither silver nor gold, but I bring with me the most precious thing given to me: Jesus Christ."
Francis arrived at a tense time for Brazil, as the country reels from sometimes violent demonstrations that began last month as a protest against public transport price hikes and mushroomed into a wave of protests against government corruption and spending for the 2014 World Cup and 2016 Olympics.
Those protests continued after Francis' arrival. Police and anti-government protesters clashed outside the government palace. About an hour after the Pope concluded his short speech, police began cracking down on the protests, firing rubber bullets to disperse the crowd.
"We've got nothing against the Pope. Nobody here is against him," said art student Christopher Creindel, 22, who was outside the government palace. "This protest is against our politicians."
- AP
