By Anthony Boadle and Ricardo Brito
BRASILIA (Reuters) - Brazil's front-running far-right presidential candidate Jair Bolsonaro is in serious but stable condition in hospital following "successful" surgery after he was stabbed while campaigning on Thursday, his running mate said.
Flavio Bolsonaro, the candidate's son, wrote on Twitter that his father had been wounded in the liver, lung and intestine. "He lost a lot of blood, arrived at the hospital ... almost dead. He appears to have stabilized now," he said.
General Antonio Hamilton Mourao, Bolsonaro's running mate, told Reuters by telephone that the candidate's condition was stable but still worrying.
"He underwent surgery, which was successful and he is doing OK," Mourao said. "But his state remains delicate."
A hospital spokeswoman in the city of Juiz de Fora in Minas Gerais state, where the attack took place, confirmed to Reuters that Bolsonaro had been undergoing surgery but provided no details on his state nor his wounds.
The attack on Bolsonaro is a dramatic twist in what is already Brazil's most unpredictable election since the country's return to democracy three decades ago. Corruption investigations have jailed scores of powerful businessmen and politicians, and alienated infuriated voters.
Violence in Brazil is rampant - the country has more homicides than any other, according to the United Nations - and political violence is common at the local level.
For instance, in the months before 2016 city council elections in Baixada Fluminense, a hardscrabble region the size of Denmark that surrounds Rio de Janeiro, at least 13 politicians or candidates were murdered before ballots were cast.
Earlier this year, Marielle Franco, a Rio city councilwoman who was an outspoken critic of police violence against slum residents, was assassinated.
But violence against national political figures, even in the extremely heated political climate that has engulfed Brazil in recent years, is rare.
The Federal Police said in a statement that it had officers escorting Bolsonaro at the time of the knife attack and the "aggressor" was caught in the act. It said the circumstances were being investigated.
Local police in Juiz de Fora confirmed to Reuters that a suspect was in custody, but they did not identify him.
"We do not know if it was politically motivated," Corporal Vitor Albuquerque, a spokesman for the local police, said by telephone.
TV images show Bolsonaro being carried on someone's shoulders in the middle of a crushing crowd of cheering supporters on one of the city's main streets when a knife was seen raised above heads just before it plunged into the candidate's body.
The pictures show Bolsonaro appearing to scream in pain, then falling backward into the arms of those around him. It took a few moments for the crowd to realize what occurred, but they quickly rushed the candidate out of the street.
Bolsonaro, who has spent nearly three decades in Congress, is a law-and-order candidate who routinely says that Brazilian police should kill suspected drug traffickers and other criminals at will. He has openly praised Brazil's military dictatorship and in the past said it should have killed more people.
Bolsonaro faces trial before the Supreme Court for speech that prosecutors said incited hate and rape. He has called the charges politically motivated.
Fernando Haddad, who will likely be the leftist Workers Party presidential candidate, said the stabbing was a "shame" and a "horror."
President Michel Temer and Bolsonaro's electoral rivals Ciro Gomes, Marina Silva, and Geraldo Alckmin all expressed outrage at the attack.
Brazil's stocks <.BVSP> and currency extended gains after the stabbing as traders bet the incident could boost support for Bolsonaro, who has tapped a University of Chicago-trained banker as his main economic adviser.
(Reporting by Anthony Boadle, Ricardo Brito and Lisandra Paraguassu in Brasilia and Brad Brooks in Sao Paulo; Additional reporting by Tatiana Bautzer and Carolina Mandl in Sao Paulo and Bruno Federowski in Brasilia; Writing by Brad Brooks; Editing by Grant McCool and Rosalba O'Brien)