Voters are also choosing a vice president and 160 representatives in the Guatemalan Congress.

Many Guatemalans expressed disappointment with their presidential choices after three opposition candidates were excluded by the authorities. A large number of null ballots were expected, and experts said it could depress turnout.

Former first lady Sandra Torres, from the National Unity of Hope (UNE) party, is tipped to win the first round but is expected to fall short of the 50 percent plus one vote needed for an outright victory in the contest, the fairness of which has come under international scrutiny.

The 67-year-old businesswoman has unsuccessfully sought the presidency twice before. She is allied with the current legislature’s governing Vamos (Let’s Go) party.

Torres finished second in the previous two presidential elections, but she and her party faced accusations of corruption and illegal campaign financing. She has denied the accusations and campaigned on a promise to bolster social programmes to address poverty throughout the country.

She is up against more than 20 other candidates, including Edmond Mulet, a career diplomat, and Zury Rios, daughter of the late dictator Efrain Rios Montt.

Mulet, 72, with the centrist Cabal (Spot On) party, is campaigning on pledges to bolster the economy and invest in healthcare, education, and security.

His campaign has been beset by accusations he was involved in an illegal child adoption operation in the 1980s, when thousands of infants and children were taken from their families and put up for adoption abroad. Mulet has adamantly denied having any part in the scheme.

Rios, 55, whose Valor (Valour) party was also part of the previous governing legislative coalition, was allowed to compete in the elections after the Constitutional Court ruled in May that a rule barring the family members of those who took power in a coup from running for office should not apply to her. She has campaigned on a tough-on-crime agenda.

The race to succeed conservative President Alejandro Giammattei, who is limited by law to one term, has been overshadowed by a court ruling to block four candidates from the ballot including the early frontrunner, businessman Carlos Pineda.

The United States and the European Union criticised the exclusion of Pineda, who called the decision “electoral fraud”.

Approximately 9.2 million Guatemalans are eligible to cast their ballots to elect the country’s next president and vice president, as well as 160 representatives in the Congress.

Hundreds of local positions are also up for grabs, as are 20 seats in the Central American Parliament.

Voting centres, which opened at 7am (13:00 GMT), are scheduled to close at 6pm (00:00 GMT on Monday).