The Brazilian president, Jair Bolsonaro, has led a raucous column of motorcycle enthusiasts through the streets of Rio in an attempt to reenergise his flagging far-right movement as public anger grows over his handling of the country’s Covid outbreak.

Thousands of flag-waving Bolsonaristas gathered outside the Olympic Park in west Rio on Sunday morning for the two-wheeled show of support before roaring east towards the southern beach districts and city centre, with Bolsonaro near the front.

As defenders of the Brazilian president assembled under a white banner reading “Legend, you are not alone!”, Bolsonaro’s detractors bashed pans and hurled profanities from their balconies in protest. Many dissenters denounced as “genocidal” his handling of a Covid epidemic that has killed almost half a million Brazilians, nearly half of the total lost in Latin America and the Caribbean.

Supporters said they had come from across the country to endorse the 66-year-old leader.

“He represents freedom, order and progress and the end of corruption,” said José Antônio do Nascimento, a 57-year-old who had travelled south from the city of Belo Horizonte and was wearing a white and red T-shirt that read: “We’re down with Bolsonaro”.

Nearby a group of leftwing and LGBT demonstrators had turned out to voice their disgust and show the Bolsonarian bikers their middle fingers.

“I feel profound sorrow,” said Marcio Vellozo, a 48-year-old law graduate. “We’ve lost nearly 500,000 lives and people are hitting the streets to celebrate. What are they celebrating?”

The crowded motorcade – which Bolsonaro’s critics called an obscenity given Brazil’s relentless coronavirus emergency – looked like an attempt to wrest back the political initiative after a dismal few weeks for the rightwing populist. Bolsonaro’s political standing has taken a severe hit since his main rival, the former leftist president Luiz Inácio Lula da Silva, burst back on the political scene in March with the restoration of his political rights.

“His popularity ratings are in freefall,” said Thaís Oyama, the author of a book about Bolsonaro who believed that the president’s response to coronavirus was largely to blame.

With a congressional Covid inquiry currently examining the Bolsonaro administration’s failure to control the epidemic or acquire sufficient vaccines, Oyama said that even Bolsonaro voters were now wondering whether their relatives would have survived had Bolsonaro responded differently.

She claimed that Sunday’s motorcycle rally was designed to project strength but actually betrayed “a certain despair” over his tumbling popularity and Lula’s reemergence.

Lula, a former union leader who has been the country’s main left-wing leader since the late 1980s, looks set to challenge Bolsonaro for the presidency in the 2022 election, with polls suggesting the leftist is in pole position.

Speaking to the Guardian last week, Lula claimed that Bolsonaro would eventually be held to account for his calamitous Covid response but recognised that his rival still had the support of a hardcore of “fanatics” representing between 15% and 20% of voters.

“These people have always existed, in any society. You have such people in England. They exist in Germany, they exist in the US and they exist in Brazil too,” Lula said of those radicals. “What we need to ensure is that the majority has the right to govern this country.”

Bolsonaristas may be a minority but they are a noisy one. Thousands of rightwing and predominantly white and male bikers, some wearing Donald Trump face masks or waving the flags of Israel and Brazil, turned out for Sunday’s procession, revving their engines all the way to its conclusion at a second world war monument near downtown Rio.

It took more than nine minutes for the entire motorcade to pass the Guardian’s position, where street hawkers sold Bolsonaro-themed paraphernalia including anti-Covid face masks stamped with Bolsonaro’s likeness and the words “my president”.

Bolsonaro was not wearing a mask when he addressed the throng from the top of a sound truck and claimed he was on a God-given mission to save Brazil. “I knew it wouldn’t be easy but all of us have a mission here on Earth,” he told his acolytes. “It’s a heavy cross to bear but He helps us to do so, as do all of you”.

Brazil’s president, who has been internationally condemned for undermining Covid containment measures and calling the disease “a little flu”, said he regretted “every single death, of whatever cause”. “But we must be strong. We have got to face this challenge. We must live and we must survive.”

Shaking his fists at the Bolsonaro-supporting bikers nearby, Vellozo said: “Our president is a 100% denialist. Trump is now out of the picture and so he is seeking to become the global leader of denialism.

“I’m not surprised by the size of [the protest],” he added. “But as a Brazilian, it disappoints me.”