Brazil's far-right candidate Jair Bolsonaro won the first round of the presidential election on Sunday, but still faces a runoff against his leftist rival Fernando Haddad later this month, while the final outcome is still hard to predict, said a Chinese expert.

The country's Superior Electoral Court said the results confirmed that voters will be heading to the polls again for the second round of the election, as neither of the two leading candidates reached 50 percent support to win outright.

According to the official result, Bolsonaro had 46 percent compared to 29 percent for former Sao Paulo Mayor Haddad, with some 91.22 percent of the votes cast being valid.

The two are scheduled to go through a runoff vote on Oct 28.

Voice of change

Guo Cunhai, researcher from Institute of Latin American Studies at the Chinese Academy of Social Sciences, said the first round result brought no big surprises.

"The number reflects the Brazilian people's voice for having a different leader to change the situation amid the unstable domestic social environment and economic downturn," he said.

However, Guo said the winner still remains unclear, especially amid the changeable voting situation.

"Judging from the current percentage of votes obtained, Bolsonaro might be the future president," he said. "But there are also many uncertainties that may affect the outcome, such as swing voters changing their choice."

He said since the number of solid supporters from both sides is not huge, it is more important to win votes and support from the swing voters during the next 20 days.

Bolsonaro said on his Facebook account that the count "was very good", and he was "sure that God will help us during the second round", claiming he is ready to unite Brazil.

"We have everything to be a great nation; we must unite our people, unite the shards the past governments transformed us into," he said. "United, we will be a great nation. Nobody has the potential we have."

Bolsonaro said he will work to get more votes in the northeastern region, where he lost in all nine states and where most of Haddad's supporters come from.

The ex-military officer from the Social and Liberal Party made savvy use of Twitter and Facebook to spread his message that only he could end the corruption, crime and economic malaise that has seized Brazil in recent years and bring back the good old days and traditional values.

Haddad, on the other hand, also called on Brazilians to unite behind him, warning that the 1988 Constitution that underpinned Brazil's young democracy was under threat. He said he had already spoken to three other candidates to join forces against the right-winger.

"There is a lot at risk in this election," Haddad told his supporters. "We want to unite all the democrats in Brazil."

Haddad has promised to roll back President Michel Temer's economic reforms that he says eroded workers' rights, increase investment in social programs and bring back the boom years Brazil experienced under his mentor, former president Luiz Inacio Lula da Silva.