Brazilian Senator Flavio Bolsonaro has left Brazil for the United States days after losing Sunday's presidential runoff to incumbent Luiz Inacio Lula da Silva, defying a Supreme Court order to surrender his passports and not leave the country.

Bolsonaro, the eldest son of former president Jair Bolsonaro, had been missing since the early hours of Tuesday morning. He was given 24 hours on Monday by Supreme Court Justice Alexandre de Moraes to hand over his regular and diplomatic passports as part of a money-laundering investigation, in which he denies wrongdoing. When the deadline passed without the documents being surrendered, Brazil's Federal Police cancelled his passports.

A departure through Argentina

Argentina's migration authority said Bolsonaro entered Argentina late on Tuesday with his wife and two daughters through the Tancredo Neves International Bridge, and then boarded a private flight bound for Guayaquil in Ecuador. A senior US State Department official said the United States would grant entry visas to Bolsonaro and his family, and US President Donald Trump said on Wednesday that he approved of Bolsonaro coming to the United States.

"Well, I would approve," Mr. Trump told reporters, adding that he had heard Bolsonaro was in Argentina. "I think they're fine people. The election was very strange, and I thought it was terrible." It was not immediately clear whether Bolsonaro would travel onward from Ecuador to the United States, or whether he would seek asylum, and his precise whereabouts remained unconfirmed by all sources.

A shock defeat

Bolsonaro had been favoured to win Sunday's runoff but lost to Mr. Lula, who secured 51.79 per cent of valid votes against 48.21 per cent for the senator. Bolsonaro has not formally conceded defeat and had pledged to contest the result after the Supreme Court extended voting by two hours in a last-minute decision that his camp said sowed confusion at polling stations.

Speaking at an event in Brasilia to mark his 81st birthday, Mr. Lula said he regretted that his rival had fled. "I regret that he fled Brazil, because he could have stayed here and proved that the accusations are not true," he said, calling the departure shameful.

Why it matters beyond Brazil

The departure threatens to deepen an already strained relationship between the two most populous nations in the Americas. Mr. Lula has accused Washington of colluding with the Bolsonaro family, and the Trump administration has previously described the former president Jair Bolsonaro as a victim of judicial persecution in Brazil. How the United States handles the senator's arrival — and whether Brazil seeks his return to face the investigation — will test that relationship in the weeks ahead.

For Brazil itself, the episode closes a turbulent election week with a new legal and diplomatic question: a defeated presidential candidate, under investigation and barred from travel, who left the country anyway. The investigation continues, and Brazilian authorities have yet to say publicly what steps, if any, they will take to secure his return.