Brazilian President Jair Bolsonaro has launched an attack on coronavirus vaccines, even suggesting that the one developed by Pfizer-BioNTech could turn people into crocodiles or bearded ladies.

The far-right leader has been sceptical of the coronavirus since it first emerged late last year, branding it "a little flu." This week he insisted he would not be vaccinated, even while launching the country's mass innoculation program.

"In the Pfizer contract it's very clear: 'we're not responsible for any side effects.' If you turn into a crocodile, it's your problem," Bolsonaro said on Thursday.

That vaccine has been undergoing tests in Brazil for weeks and is already being used in the United States and Britain.

"If you become superhuman, if a woman starts to grow a beard or if a man starts to speak with an effeminate voice, they will not have anything to do with it," he said, referring to the drug manufacturers.

When launching the immunization campaign on Wednesday, Bolsonaro also said it would be free but not compulsory.

But the Supreme Court on Thursday ruled that the vaccine was obligatory, although could not be "forced" on people.

That means authorities can fine people for not being vaccinated and ban them from certain public spaces, but not force them to take it.

Brazil has recorded more than 7.1 million cases and almost 185,000 deaths from Covid-19 amongst its 212 million population.

Bolsonaro said that once a vaccine has been certified by Brazil's regulatory agency Anvisa, "it will be available for everyone that wants it. But me, I won't get vaccinated."

"Some people say I'm giving a bad example. But to the imbeciles, to the idiots that say this, I tell them I've already caught the virus, I have the antibodies, so why get vaccinated?"

There have been a small number of cases of apparent reinfection although there is no certainty over whether a person can be reinfected or how long immunity lasts.

Bolsonaro caught the virus in July but recovered within three weeks.

Brazil is in the middle of a second wave of coronavirus infections.

After peaking in June to August cases had been dropping but that changed in November.

On Thursday, Brazil surpassed 1,000 daily deaths from covid-19 for the first time since September.