Early official results showed former congresswoman Keiko Fujimori narrowly in the lead with 17.17 per cent closely followed by right-wing former Lima mayor, Rafael Lopez Aliaga with 16.97 per cent, with 37 per cent of votes counted, according to Peru's electoral body, ONPE.
Exit polls on Sunday had shown Fujimori, daughter of ex-president Alberto Fujimori who was imprisoned for human rights abuses, in the lead, although Lopez Aliaga emerged in the lead earlier in the count underlining the fluidity of the race.
Years of political turmoil in the Andean nation have eroded confidence in institutions and left voters deeply disillusioned.
With no clear frontrunner and all major candidates polling well below the 50 per cent needed to win outright, a June 7 run-off appeared likely -a scenario that could prolong uncertainty in the world's third-largest copper producer at a time of rising crime and intensifying competition for influence between the United States and China.
"I want to express my solidarity with the citizens who today were denied the opportunity to exercise their right to vote," Fujimori said in a brief statement, adding that she would begin a new campaign for the run-off from Monday.
Delays to polling stations opening were reported in some areas on Sunday morning, centred in the capital Lima,following logistical issues involving a contractor responsible for the distribution of electoral material.
The disruptions prompted authorities to extend voting hours by one more day for more than 50,000 people who were unable to cast their ballots.
Roberto Burneo, head of Peru's electoral authority, said legal action would be taken against the company responsible for distributing the voting materials.
Since 2018, Peru has cycled through eight presidents, fuelling scepticism that any new administration will last a full five-year term following a dizzying turnover driven by impeachments, corruption scandals and weak governing coalitions that have paralysed decision-making.
Political distrust has fuelled a crowded field spanning the ideological spectrum, including seasoned politicians, a far-right businessman and a television comedian.
Among the best known is conservative Fujimori, making her fourth presidential bid after reaching the run-off in all three previous races.
Educated in the US and leader of the powerful Popular Force party in Congress, Fujimori has framed herself as a guarantor of order and economic stability, appealing to voters alarmed by surging violent crime.
Her candidacy remains polarising, however, due to her family legacy and past legal troubles.
Former Lima mayor Lopez Aliaga, a wealthy businessman with socially conservative views, campaigned on an ultra-conservative platform and had seen support fluctuate in the weeks before the election.
Centre-left Jorge Nieto, who has pitched himself as a unifying figure with institutional experience, was polling in third place late on Sunday, with 14.1 per cent of the vote.
Ricardo Belmont, a former Lima mayor running for the centre-left Civic Works Party, saw a late rise in support, elevating him in polls in recent days.
Public insecurity has emerged as the dominant theme of the campaign.
Homicides and extortion have climbed in recent years, driven in part by drug trafficking and illegal mining.
Most leading candidates have proposed expanding the role of the armed forces in internal security.
Whoever advances to the run-off will face a fractured Congress and newly reinstated Senate, which might complicate efforts to pass legislation and raise the risk of renewed impeachment battles.
