Electoral authorities in the southern Mexican state of Guerrero decided to annul the elections in the municipality of Tixtla Sunday, after teachers trainees from Ayotzinapa and relatives of the 43 students missing from the school burned more than 20 percent of the electoral boxes and ballots deployed for that area.

Mexico is holding midterm elections this Sunday, more than 83 million people eligible to vote for candidates to the 500 seats in the lower house of Congress, nine of 31 governorships and hundreds of mayorships and local posts.

However the electoral process has been marred by protests and calls for boycott, as anger over violence and corruption in the country rises.

Since early this year, the relatives of the disappeared students have demanded the suspension of local elections in Guerrero state, arguing that the candidates have ignored their calls for justice regarding the case.

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Meanwhile the National Electoral Institute condemned the violence, saying that a legal action should be taken. The Mexican electoral body confirmed that the municipality elections in the area had been canceled due to the disturbances, however.

Tens of thousands of Mexican troops and federal police were deployed to guard polling stations in restive southern states Oaxaca, Chiapas and Guerrero, where teachers' unions and activists vowed to block the vote, in what has been Mexico's most violent elections in years. Leading up to the vote, at least 11 candidates had been killed.

The elections are expected to have a lower turnout than usual, given the widespread social unrest over the corruption scandals, a lackluster economy and human rights concerns that have prominent during President Enrique Peña Nieto's three-year-old government.