A front-runner in Brazil's presidential election, Jair Bolsonaro, has been stabbed during a campaign rally.
The far-right politician was attacked in the city of Juiz de Fora in the south-eastern state of Minas Gerais.
He underwent surgery for injuries to his liver and intestines but is now stable, his son said.
The controversial politician, who has outraged many in Brazil with racist and homophobic comments, has performed strongly in recent polls.
Polls suggest he would get the most votes in next month's presidential elections if former president Lula da Silva fails in his attempt to overturn a ban on him standing.
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Footage of the incident shows Mr Bolsonaro making a thumbs-up gesture and being held aloft by supporters when he appears to be stabbed with a knife.
He then doubles over with pain and his supporters quickly lower him to the ground and bundle him into a car.
After the attack, his son Flavio initially tweeted that the wound was "only superficial", but he gave a more sombre assessment two hours later.
"Unfortunately it was more serious than we had expected," he wrote. "The perforation reached part of the liver, the lung and the intestines. He lost a lot of blood, arrived at the hospital with a (blood) pressure of 10/3, almost dead. His condition now seems stabilised. Pray, please!"
Police say a suspect has been arrested. He was named as Adelio Obispo de Olivei
Mr Bolsonaro's backers see him as a strong leader who would crack down on crime.
The 63-year-old, who is representing the Social Liberal Party (PSL), is followed by millions of Brazilians on social media, and many refer to him as the "Brazilian Trump".
He also supports loosening gun control laws, and is backed by millions of evangelical Christians for his uncompromising anti-abortion stand.
How did he become a presidential contender?
Brazil had just returned to democracy, and in 1989 held its first free presidential election.
Few imagined at that time that he could become a serious contender in a presidential poll. But the collapse of the Workers' Party government and the impeachment of President Dilma Rousseff two years ago revealed the extent of political divisions in the country.
Mr Bolsonaro's outspoken rhetoric and his defence of law and order appealed to many who blamed the left for corruption and the economic crisis.
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In 2011, he told Playboy magazine that he would be "incapable of loving a gay son" and that he would rather see such a son of his "die in an accident".
In 2015, he was fined for saying in a newspaper interview that Congresswoman Maria do Rosario was "not worth raping; she is very ugly".
He is currently being investigated for alleged racism over derogatory remarks he made about Afro-Brazilians.