Charges of fake news are heating up the presidential race ahead of Brazil's October 28 runoff, with the centre-left candidate accusing his rival's campaign of defaming him with false stories on social media and messaging apps.
A fact-checking group said that Fernando Haddad has been targeted by a wave of false allegations, some accusing him of planning to shut down churches and distribute textbooks teaching children to be gay.
Haddad blamed his adversary, far-right candidate Jair Bolsonaro, for planting or failing to condemn the falsehoods.
"The lies come from him (Bolsonaro), so he will not accept any ethical commitment. He will continue to slander, insult," Haddad said.
He said his campaign had managed to have 33 videos removed from social media sites. "One had 3 million views when it was removed. We try to stop it, but people watch them."
Haddad on Monday asked Bolsonaro to jointly sign a commitment against spreading fake news before the runoff, but Bolsonaro rejected the idea, calling Haddad "a scoundrel" in a Twitter post.
Haddad said on Tuesday the refusal was "a proof of dishonesty".
Bolsonaro, a former army captain, won Sunday's first round of voting with 46 per cent.
Former Sao Paulo Mayor Haddad, who was hand-picked by jailed former President Luiz Inacio Lula da Silva to represent the Workers' Party, came second with 29 per cent.
Later in an interview with TV Band, Bolsonaro said he wants to fight false news against him in Brazil's northeast, without giving further details.
Bolsonaro said he regretted the killing of a Haddad voter in Salvador by one of his supporters but he called it "an isolated incident".
