Polls are due to open across Mexico after a campaign marred by some of the worst political violence in the country for decades, wrote BBC.

More than 130 candidates and political workers have been killed since campaigning began in September.

The presidential frontrunner is Andres Manuel Lopez Obrador, the left-wing former mayor of Mexico City who has pledged to crack down on corruption.

He could oust the two parties that have governed Mexico for nearly a century.