Flavio Bolsonaro has said a Supreme Court justice had banned him from leaving Brazil, one day after he lost the country's presidential election and refused to concede defeat.
The right-wing senator received 48.2 percent of the vote compared to 51.8 percent for incumbent Luiz Inacio Lula da Silva.
"I was served with an order to hand over my passports, and I am also banned from leaving the country," he said in a video posted to Instagram on Monday.
Bolsonaro, the son of jailed ex-leader Jair Bolsonaro, denounced "a clear attempt to intimidate me."
The senator is under investigation for alleged corruption and money laundering during the financing of a biopic about his father. He denies any wrongdoing.
'Organise opposition'
The 45-year-old said the decision to seize his passport stems from a statement made by his brother, US-based former lawmaker Eduardo Bolsonaro, that Flavio would have to leave Brazil if he lost the election.
"I never said that," the defeated candidate insisted in the Instagram video.
Bolsonaro reiterated that he would seek to annul the election, arguing that an extension of voting hours on Sunday favoured Lula, despite having also requested the measure.
He also promised to lead the resistance to Lula's government, however.
"To withstand the chaos, I'm going to organise the opposition," Bolsonaro said.
Lula won a historic fourth term in Sunday's election in a surprise result that defied polls. Bolsonaro refused to accept defeat and said he would ask for the result to be annulled.
