In a press conference on Monday, Fujimori said a series of irregularities were detected in the elections held on Sunday that worried her and that it is "important to highlight it".

She also urged citizens to report any cases of which they were aware.

The candidate has secured 49.7 per cent of the votes against Castillo's 50.2 per cent, with 94.4 per cent of the ballots counted by the country's elections agency.

Among the irregularities that the Popular Force candidate claims are the challenges to the records in which she says she had a higher number of votes than her rival, training talks by Free Peru urging staff to report earlier in order to ensure votes, and a complaint against an employee of the party who fraudulently marked 87 cards.

"There is a clear intention to boycott the will of the people," Fujimori said, asking that similar cases be shared on social media under the hashtag FraudeEnMesa.

"It's not that we are concerned about our candidacy, it's about defending the future of our country," she added.

Fujimori's running mate Luis Galarreta said at the press conference that in Puno, a family that supported Castillo presented themselves as officials at one of the local polling booths.

He mentioned that there were more than 1200 contested ballots on which Fujimori allegedly received the vote.

Galarreta argued that the outcome would be different if those votes had not been contested.

Meanwhile, Fujimori said that the current difference of 0.5 per cent between her and Castillo "keeps us optimistic".

She expressed confidence that the result would be evened out once the overseas ballots were counted.

Australian Associated Press