Bogota, May 30 (IANS): The Colombian presidential election is heading for a runoff on June 19, which will see the two main contenders, former Bogota Mayor Gustavo Petro and construction magnate Rodolfo Hernandez, battle it out for the top post.

With 99.95 per cent of the ballots counted from Sunday's first round of voting, Petro, also a former leftist rebel, received 8,526,466 votes, followed by Hernandez with 5,952,783, reports Xinhua news agency.

Alexander Vega, Colombia's national registrar, confirmed that the results had been double verified and that the Registrar's Office is prepared for the June 19 runoff.

"According to the trend, of course (there is a second round) and we are going to prepare ourselves with the same guarantees, transparency, and security of the process," Vega told reporters.

The official said that during the second round, international monitors would be present.

If the 62-year-old Petro wins, he will be the first left-wing President in Colombia's history, according to a BBC report.

He has promised to fix deep inequalities and switch the country's reliance on fossil fuels to clean technology.

Meanwhile, Hernandez, 77, has campaigned on an anti-corruption ticket, despite being under investigation for allegedly favouring a company his son had lobbied for, the report said.

Outgoing President Ivan Duque was not allowed to contest again as per the Constitution which only permits a single-term.

The new President will assume office on August 7.