Brazil's far-right President Jair Bolsonaro maintained an increasingly loud silence Monday after his election defeat, failing to acknowledge his loss to veteran leftist Luiz Inacio Lula da Silva -- who faces a tough to-do list.

Twenty-four hours after the close of voting in Sunday's deeply polarizing runoff election, Bolsonaro had still not recognized the outcome -- raising fears he could try to challenge it, with potentially turbulent results for the country.

Charismatic but tarnished ex-president Lula defeated Bolsonaro by the narrowest margin in Brazil's modern history -- 50.9 percent to 49.1 percent -- to return for an unprecedented third term at the helm of Latin America's biggest economy from January 1.

After a dirty, divisive campaign that left the country of 215 million people split in two, the 77-year-old leftist icon now faces a laundry list of challenges, including a struggling economy, rampant destruction of the Amazon rainforest, and a powerful and angry far-right.

But first, there is the giant question mark over whether Bolsonaro will accept defeat.

The far-right president has not spoken publicly or on his beloved social media accounts since the result was announced, after months of alleging fraud in the electoral system and a conspiracy against him.

The transition period got off to a tense start as pro-Bolsonaro truckers and protesters blocked highways in at least 11 states across the country Monday, burning tires and parking vehicles in the middle of the road to halt traffic.

Wearing the yellow and green of the Brazilian flag -- which the outgoing president has adopted as his own -- the protesters wielded pro-Bolsonaro signs and sang the national anthem, before gradually being broken up by the authorities in some areas.

On Monday night Judge Alexander de Moraes of the Supreme Court ordered police to disperse the blockades immediately. He was acting in response to a request by a transport federation that complained it was losing business.

Markets were volatile, but reacted favorably overall to the election: after dipping slightly, stocks were up 1.3 percent in afternoon trading in Sao Paulo, and the Brazilian real gained more than two percent against the dollar.