Mexico City, Mexico - Enrique Pena Nieto, the youthful candidate of the party that governed Mexico for decades, has claimed victory in the country's presidential election.

The first results posted by the electoral institute said Mr Pena Nieto had around 38 per cent of the vote against around 32 per cent for his nearest rival, leftist Andres Manuel Lopez Obrador from the Party of the Democratic Revolution (PRD).

The margin was not as wide as in exit polls, but was difficult to overcome.

The win will mark a stunning comeback for Mr Pena Nieto's centre-left Institutional Revolutionary Party (PRI), which ruled for seven decades until 2000 through a mixture of patronage and selective repression.

Mr Pena Nieto, 45, is an ex-governor of the populous state of Mexico, located just west of the capital, and is married to glamorous telenovela star Angelica Rivera.

He entered the PRI headquarters in Mexico City to a hero's welcome soon after the results were announced.

"Presidente! Presidente!" the crowd chanted.

"The day of voting has ended. The country now demands ... the unity of all Mexicans," he said, then thanked the other candidates by name for what he said was their contribution to democracy.