Students of Ayotzinapa Teacher Training College Raul Isidro Burgos clash with riot policemen on the outskirts of Tixtla, in the state of Guerrero, on Wednesday. Reuters

Protests in Mexico were ramping up this week as activists still angry over the case of the 43 students who went missing Sept. 26, 2014, vowed to stop the country's midterm elections. Three policemen and one student were injured during a demonstration Wednesday in Ayotzinapa, a city in the Guerrero state where the group of students disappeared, El Sol de Mexico reported. But despite the unrest, the National Electoral Institute indicated the elections would continue as planned on Sunday.

Nine buses' worth of protesters Wednesday gathered in Ayotzinapa to travel to Chilpancingo, Guerrero's capital, to express their discontent with how the government handled the high-profile case of the 43 missing students who vanished last fall. Police confronted the demonstrators, and riots broke out, with officers using tear gas and batons to control the crowd. Protesters threw Molotov cocktail bombs and stones, Uno Más Uno reported.

The 43 missing students were on their way to protest an education speech by the mayor's wife in Iguala, Guerrero, last year when they were intercepted by police. The police then turned over the group to a gang, which is thought to have killed the 43 men and disposed of their remains. Only one victim's body has been identified, but the rest were presumed dead in January. In response, relatives and friends of the missing have taken aim at what they see as an ineffective investigation and corrupt government.

With Sunday's vote looming, they were urging people to boycott the elections. They weren't alone -- on Monday, teachers' union members in Oaxaca attacked electoral offices to protest education reform.

Overall, more than 21 people have died in connection with the elections so far. "We must stop voting for narco-politicians in our country,” protester Francisco Sánchez Nava told the Buenos Aires Herald. “It is the only way we have of changing things in our country where there are nearly 30,000 missing people.”

Lorenzo Córdova, the chairman of the National Electoral Institute, said Wednesday that the organization was ready to proceed as scheduled, Crónica reported. "We are en route to install all of the [electoral] boxes, even in Oaxaca and Guerrero, but this will depend on the security situation there," Cordova said. He ordered alternate polling locations in those areas of unrest.