Mexican presidential candidate Enrique Pena Nieto has comfortably won Sunday's presidential elections, exit polls carried out by two TV stations showed.

Mexican presidential candidate Enrique Pena Nieto?[File photo]

The exit polls showed that Pena Nieto of the Institutional Revolutionary Party (PRI) won 42 percent of the vote, compared to 31 percent for his nearest rival Andres Manuel Lopez Obrador of the Party of the Democratic Revolution.

Despite massive student protests against the return of the PRI, a long-standing ruling party, voting around the country was marked by relative calm.

The Federal Electoral Institute (IFE) reported that voting had progressed "normally" at 99.78 percent of the 143,132 voting stations throughout the country. Some 600 stations failed to open, the IFE said, without providing further details.

Some minor incidents were reported, including several investigations into alleged voting irregularities in four states -- Mexico, Veracruz, Jalisco and Zacatecas -- while one person was reportedly detained for purchasing voter IDs.

In northern hotspots, such as Nuevo Laredo, navy and army troops were dispatched to patrol the streets and guarantee voters' safety.

Voter turnout was reported to be high at most polling stations around the country, despite seasonal afternoon rains, especially in central Mexico.

TV cameras followed the presidential candidates throughout the day as they cast their votes.

After casting his ballot, Pena Nieto said "I hope the Mexican people are the real winners in this election."

Sunday's general elections were the largest in Mexican history with 2,127 positions at stake, including the president, senators and deputies to Congress, six governors and the mayor of Mexico City.