Figure caption, ByIone WellsReporting fromBrasília and Hafsa KhalilUpdated 2 hours agoBrazil's President Luiz Inácio Lula da Silva has won a fourth term in office in a dramatic comeback over his right-wing challenger Flávio Bolsonaro. 79% of votes, becoming the first president since Brazil's return to civilian rule in 1985 to be elected after losing the first round of voting.

Flávio Bolsonaro, the son of convicted former president Jair Bolsonaro, has so far refused to recognise the result and called for it to be annulled. World leaders have congratulated Lula on his re-election.

Bolsonaro's rejection comes as no surprise to observers. His father did the same.

But a challenge appears unlikely to succeed. Firstly, it seems to centre on the unprecedented decision by the Supreme Court Justice Cristiano Zanin to extend voting nationwide by two hours.

Some Bolsonaro fans are pointing out that Zanin was once Lula's lawyer and alleging bias. But both teams had requested an extension to voting times - Lula's had argued that voters in São Paulo and Bahia could not get to the polling stations because of a lack of buses, while Bolsonaro's campaign cited heavy rain in some areas in the south of the country and in São Paulo as their reason.

Both knew every vote would count and did not want their side to miss out. The president of the Supreme Electoral Court Kássio Nunes Marques – appointed by Jair Bolsonaro – confirmed Lula's victory and said that the voter extension did not change the outcome of the race.

4 million votes - makes the result more difficult to challenge. But Lula's camp gained momentum ahead of election day, focusing on boosting voter turnout after 33 million people did not vote in round one.

Sunday saw the largest drop in abstention between the two rounds of a presidential election since 1989. As his disconsolate supporters left the house in Brasília where their candidate had been watching the result, Lula took to the streets in São Paulo to celebrate."

This, my fourth term, will be the best of any president in the history of this country," the former metal worker told supporters. " It will be the one in which I listen most to the Brazilian people."

After pulling off this victory, Lula faces big hurdles: a divided country, an opponent that won't recognise the result, and a hostile Congress packed full of Bolsonaro allies. Markets reacted negatively to the unexpected outcome.