The EU’s election observer said the vote met democratic standards despite fraud allegations.

Peru’s presidential election result will not be finalised until mid-May, with challenged ballots from last Sunday’s vote still being reviewed, says the electoral authority.

With 93 percent of ballots counted, right-wing candidate Keiko Fujimori leads with 17 percent, according to officials.

Under Peru’s electoral system, the top two candidates advance to a second-round runoff. A close contest has emerged for second spot between left-wing candidate, Roberto Sanchez on 12 percent, and ultra-conservative Rafael Lopez Aliaga close behind on 11.9 percent.

The margin between the two widened slightly on Saturday to about 13,600 votes.

Yessica Clavijo, secretary general of the National Jury of Elections (JNE), said the delay was due to the review of more than 15,000 challenged ballots. About 30 percent concern the presidential race, the rest relate to legislative elections.

Lopez Aliaga, a former mayor of the capital Lima, has been the most vocal critic of the delay. He has alleged fraud without presenting evidence and called for the election to be annulled. He urged supporters of his Popular Renewal Party to protest on Sunday.

Sanchez also criticised the election process, telling reporters: “These serious organisational issues must be investigated and there must be appropriate sanctions”.

A record 35 candidates ran for president in Peru, a country that has faced years of political instability. Four of its last eight presidents have been impeached by Congress.

Voting was disrupted by delays in the delivery of election materials, forcing authorities to extend polling into Monday in parts of Lima.

Despite the setbacks, the European Union’s election observer mission said the vote met democratic standards. On Friday, prosecutors raided a warehouse belonging to the National Office of Electoral Processes (ONPE), the body responsible for organising the election. Four officials have been reported to the JNE over alleged offences linked to voting rights.