Mexico City – Millions of voters have headed to the polls in Mexico, in what is being billed as the largest election in the country's history.

More than 3,400 posts are up for grabs on Sunday, including the presidency and all the seats in the two houses of Congress.

Polling stations opened at 13:00 GMT. The last voting centres were set to close at 01:00 GMT on Monday.

Results are expected later on Monday. 

Three issues have defined the landmark race: security, corruption and poverty.

Mexico has slipped to 135th out of 180 countries in the Transparency International Corruption index.

A 2018 poll showed that 64 percent of the country's population believes the government isn't doing enough to combat corruption, and many Mexicans are sick of a political class that has become synonymous with pocket-lining and impunity.

Many are also becoming increasingly concerned about the country's crime rates. Last year was the most violent on record and 2018 is set to surpass that with four people killed every hour in the month of May alone, according to government figures.

Poverty levels are also topping voter's minds. More than 50 million of the country's 127.5 million people live below the poverty line. About one percent of the country's population holds a third of its wealth, according to a 2017 study by CEPAL - a regional economic commission of the UN.

Concern over these issues has seemingly helped frontrunner Andres Manuel Lopez Obrador. 

Agencies