Protesters clashed with police outside the Mexican Congress in Mexico City on Saturday, as the country’s new president, Enrique Pena Nieto, took the oath of office.

Hundreds of demonstrators threw Molotov cocktails, firecrackers and rocks at security forces, who responded by using tear gas to disperse the crowd.At least two protesters were injured, one seriously and a police officer with a bleeding face was taken for medical treatment, according to law enforcement agencies.Mexican authorities erected security barriers around the Congress several days ago in anticipation of protests by groups opposed to Nieto and the return of the Institutional Revolutionary Party (PRI) to power.Forty-six year old Nieto, who will have the top job during the next six years, won the presidential election on July 1st by a narrow margin, with his victory has exposed deep divisions within the Mexican society.The president-elect has took over at midnight in a symbolic ceremony after campaigning as the new face of the PRI, repentant and restructured after the party was voted out of the presidency in 2000. The PRI had ruled for 71 years with a mix of populist handouts, graft and rigged elections.Rioters clash with police officers outside of the Congress building before the inauguration ceremony of incoming Mexican President Enrique Pena Nieto on December 1, 2012, in Mexico City (AFP Photo / Pedro Pardo) After the oath-taking, the new president delivered his inaugural speech at the historic National Palace in the city's downtown, promising to govern democratically with transparency. But his first act in charge shows a strong link to the past. In announcing his Cabinet on Friday, he turned to the old guard as well as new technocrats to run his administration.Nieto has pledged to make economic growth and job creation the centerpiece of his administration, with campaign manager and long-time confidant Luis Videgaray the key person. Videgaray, a 44-year-old economist with a doctorate from the Massachusetts Institute of Technology, will lead the treasury department.Miguel Angel Osorio Chong, a 48-year-old former state governor who is known as a political operator and deal maker, has been named secretary of the interior, a post that will play a key role in security matters.The new president has also promised to push for reforms that could bring major private investment into Petroleos Mexicanos, or Pemex, the crucial state-owned oil industry, which is currently struggling.Rioters clash with police officers outside of the Congress building before the inauguration ceremony of incoming Mexican President Enrique Pena Nieto on December 1, 2012, in Mexico City (AFP Photo / Pedro Pardo)Policemen stay on alert as demonstrators protest outside the Congress in Mexico City during the inauguration of Mexican President Enrique Peña Nieto, on December 1, 2012 (AFP Photo / Pedro Pardo)A demonstrator throws stones at the police during a protest outside the Congress in Mexico City during the inauguration of Mexican President Enrique Peña Nieto, on December 1, 2012 (AFP Photo / Ronaldo Schemidt)A protestor holds a Mexican flag with an anti-PRI (Institutional Revolutionary Party in Spanish) sign drawn on it during clashes with police officers outside of the Congress building before the inauguration ceremony of incoming Mexican President Enrique Pena Nieto on December 1, 2012, in Mexico City (AFP Photo / Pedro Pardo)