Enrique Pena Nieto was sworn in Saturday as Mexican president, in an inauguration marking the return to power of the Institutional Revolutionary Party that governed the country from 1929-2000, dpa reported. Pena Nieto, 46, will have among his main tasks the fight against organized crime violence, which has claimed more than 60,000 lives in Mexico over the past six years. He is also expected to seek an opening of the state oil monopoly Petroleos Mexicanos to private capital. Pena Nieto formally took over the Mexican presidency in a midnight ceremony Saturday morning (0600 GMT), before the swearing in ceremony. "With the first minute of this day, the new administration is back in office," Pena Nieto said. Outgoing president Felipe Calderon handed over a flag to Nieto, who will return the Institutional Revolutionary Party to power after a 10-year gap from the presidency. The student group YoSoy132 and others demonstrated against Pena Nieto in central Mexico City. The centrist Pena Nieto won the July 1 election with 38 per cent of the votes, nearly 7 percentage points more than leftist Andres Manuel Lopez Obrador. Mexican presidents are limited to a single six-year term.