A far-left union leader and teacher has taken a surprise, though slim, lead in Peru's presidential election, and will likely face a rightwing rival in a runoff in June, incomplete results showed Monday.

With nearly 90 percent of ballots counted by Monday evening, leftist Pedro Castillo was in the lead with 18.83 percent -- much higher than predicted by opinion polls which had not even placed him in the top five.

He will likely square off on June 6 against corruption-accused Keiko Fujimori, a rightwing populist who has 13.21 percent, according to results released by the ONPE electoral office. It will be Fujimori's third shot at the top job.

Sunday's election, held in Peru's worst week of the coronavirus pandemic, saw no single candidate able to fire up crisis-weary voters and muster a decisive 51-percent majority.

As some lined up to vote, others queued for oxygen refills for loved ones battling coronavirus infection
As some lined up to vote, others queued for oxygen refills for loved ones battling coronavirus infection AFP / ERNESTO BENAVIDES

With the count not yet finalized, economist Hernando de Soto, and celibate staunch Catholic Rafael Lopez Aliaga -- both on the right of the spectrum -- remained hot on Fujimori's heels.

"The change and the struggle are just beginning," said 51-year-old Castillo, who was virtually unknown until 2017, when he led thousands of teachers in a protracted national strike that resulted in government compromise.

He represents the small far-left Free Peru party, and has made campaign promises to eject "illegal foreigners" who commit crimes, bring back the death penalty, and have the government take control of Peru's energy and mineral resources.

"With Castillo we have an anti-establishment left; socially conservative and anti-free market," political scientist Carlos Melendez told AFP.

Just over 25 million Peruvians are set to turn out to vote just days after the country of 33 million people reported a daily record April 7, 2021 of 314 coronavirus deaths
Just over 25 million Peruvians are set to turn out to vote just days after the country of 33 million people reported a daily record April 7, 2021 of 314 coronavirus deaths AFP / ERNESTO BENAVIDES

Fujimori, daughter of jailed ex-president Alberto Fujimori, faces charges brought against her by Peruvian prosecutors for allegedly taking money from scandal-tainted Brazilian construction giant Odebrecht to fund her presidential bids in 2011 and 2016.

If the leader of the Popular Force beats Castillo in June, the charges will be suspended until after her term as Peruvian law which exempts sitting presidents from prosecution.

Main candidates in Peru's April 11 presidential election
Main candidates in Peru's April 11 presidential election AFP / Tatiana MAGARINOS

For Ipsos Peru chief Alfredo Torres the second round will be deeply polarized.

"There is an anti-Fujimori sentiment in one section of the population and an anti-communist sentiment in another," he said.

Sunday's election, with some 25 million eligible voters and 18 candidates, was held one day after Peru reported a record 384 deaths from Covid-19 in 24 hours.

As some Peruvians lined up to vote -- which is mandatory -- others queued for oxygen refills for ill relatives battling Covid-19.

An election worker checks the temperature of a Quechua indigenous person arriving to vote at a polling station in the remote rural village of Capachica, in Puno, Peru, during general elections on April 11, 2021, amid the Covid-19 pandemic
An election worker checks the temperature of a Quechua indigenous person arriving to vote at a polling station in the remote rural village of Capachica, in Puno, Peru, during general elections on April 11, 2021, amid the Covid-19 pandemic AFP / Juan Carlos CISNEROS

Almost a third of voters had declared themselves undecided.

Many said they turned out, despite fear of infection, merely to avoid the fine of 88 soles (about $24) for not voting.

Peru's government had decided to press ahead with elections as South America battles a surge in infections fueled by new virus variants believed to be more contagious.

The coronavirus has killed more than 54,600 in the country of 33 million people.

Six of Peru's 18 presidential candidates, including Castillo, have contracted the virus.

Despite the pandemic outlook, election campaigning had continued until Thursday, with candidates drawing hundreds of followers to rallies.

Apart from dealing with the health crisis, the future president will have a full in-tray with deep economic decline on top of the pile.

The uncertain outcome of the vote had the markets worried, and the Peruvian sol plunged to a record low 3.8 to the US dollar last month.

Peru has been in recession since the second quarter of last year after coronavirus lockdowns shuttered businesses and crippled the all-important tourism sector.

Its economy contracted more than 11 percent in 2020, four million people lost their jobs and another five million dropped into poverty.

On the Lima Stock Exchange, the S&P/BVL Peru General Index, a broad benchmark, fell 2.29 percent on Monday and the dollar rose slightly to 3.64 soles.

The country has also been convulsed by political upheaval driven by claims of corruption at the highest echelons.

Whoever is sworn in on July 28 will be Peru's fifth president in three years, after three fell within days of each other in November 2020 amid protests that left two people dead and hundreds injured.

Peruvians also voted for 130 members of Congress.