TEGUCIGALPA - Initial election results released early Monday in Honduras showed opposition candidate Salvador Nasralla leading President Juan Orlando Hernandez, after a tense evening that saw both men declare themselves the winner before official numbers were announced.

With 57 percent of the ballots counted, the leftist Nasralla had claimed 45.17 percent of votes compared to Hernandez's 40.21 percent, according to the country's Supreme Electoral Tribunal (TSE).

The opposition has denounced the Constitutional Court's decision to allow Hernandez to run again for president despite a one-term limit, a move that has sparked fears of a crisis in the crime-racked country.

Minutes before the initial figures were released, Hernandez, 49, reassured his supporters in the capital Tegucigalpa that he was ahead, after having already declared himself the winner.

Backers of the 64-year-old Nasralla - who represents the Alliance Against the Dictatorship coalition - meanwhile chanted victory slogans and carried red flags.

"We defeated the dictatorship and defeated the fraud, I knew we could win," said Julio Lainez, a 22-year-old student.

But upon hearing the preliminary official results Hernandez said they were "not conclusive," claiming they included only urban areas.

"We have to be careful, patient, and take the process until the end," he said.

An estimated six million people were eligible to cast ballots, electing not just a president but also members of Congress, mayors and members of the Central American Parliament.

Though both candidates proclaiming themselves president had stoked fears of unrest, election observers said the voting process had been smooth.

"What we have seen so far has been positive," said Marisa Matias, a European parliament observer from Portugal, one of 16,000 monitors.

Hernandez's conservative National Party - which controls the executive, legislative and judicial branches of government - contends that a 2015 Supreme Court ruling allows his re-election.

The opposition has denounced his bid, saying the court does not have the power to overrule the 1982 constitution.

Hernandez's main rivals - former TV anchor Nasralla and Luis Zelaya, 50, of the right-leaning Liberal Party - had both said before the vote that they would not recognize a Hernandez victory.

"It's an atypical electoral process with an illegal re-election," said Zelaya after voting.

Nasralla, while visiting voting stations around the capital to rally his supporters, urged them to be vigilant for signs of fraud.

"They are out here offering poor people food, roof tiles or cement in exchange for their vote," he complained.

"I tell them that that's how they are going to stay poor. I am going to create jobs for them."

Hernandez cast his vote early in his home town of Gracias, in the country's mountainous west, accompanied by his daughter and several National Party deputies.

"Four more years," supporters chanted as he arrived. Hernandez told reporters he had been up early, messaging organizers to try and ensure the elections ran well.

Honduras, in the heart of the "Northern Triangle" of Central America where gangs and poverty are rife, has one of the highest murder rates in the world, though it has fallen during Hernandez's tenure.

What credit he claims from that progress is counterbalanced by tensions from a 2009 coup.

That year, then-president Manuel Zelaya was deposed by the armed forces, with backing from the right and from powerful businessmen, for nudging closer to Venezuela's Hugo Chavez.

Zelaya - no relation to the Liberal Party candidate - was accused of wanting to change the constitution to seek a second term.

Some analysts warned tensions could boil over because of the president's desire to hold on to power.

"For the first time, it's not a race between conservatives and liberals, but between a dictatorship and democracy," said Victor Meza, a political analyst at the Honduras Documentation Center.

Hernandez's top rivals accused the electoral board of preparing poll fraud to declare the incumbent president the victor. The TSE denies that.

Apart from the presidential election, Sunday's balloting will also decide the country's three vice presidential posts, the 128-seat congress, 20 representatives in the Central American Parliament and the mayors of 298 municipalities.