Mexico's Enrique Peña Nieto has taken over as the nation's new president, bringing the old ruling party back to power for the first time in 12 years.
The new face of the Institutional Revolutionary Party was sworn in Saturday after winning July's presidential election. But the swearing-in ceremony was marred by protests both inside and outside the congressional chamber where he took the oath of office.
Leftist lawmakers inside the chamber displayed banners against Peña Nieto, including one declaring Mexico in mourning. Outside, thousands of protesters gathered around the metal barricades surrounding the Congress building. Clashes erupted as some of the demonstrators threw Molotov cocktails and police fired tear gas to disperse them. At least 20 people were reported injured, including police.
The PRI ruled Mexico for 71 years until 2000, when it was voted out and replaced by the conservative National Action Party.
Peña Nieto's predecessor, Felipe Calderon, formally transferred power to him in a brief symbolic ceremony shortly after midnight in Mexico's historic National Palace.
Calderon is perhaps best known for launching Mexico's U.S.-backed military crackdown on drug gangs in 2006. More than 60,000 people have been killed since the crackdown began.
Peña Nieto said he is committed to continuing the fight against drugs, but he is calling for a new strategy focused on reducing drug violence. He also has pledged to boost Mexico's economic growth. Last year, the Mexican economy grew faster than Brazil's.
In a move considered a consensus builder, Peña Nieto has chosen some members of Calderon's administration for his Cabinet. The Cabinet was introduced to the media Friday in Mexico City.
Meanwhile, on Tuesday, the newly-elected president met with President Barack Obama at the White House where the two leaders discussed an array of bilateral and regional issues. Washington has said it is committed to working with Mexico to develop a "secure and efficient 21st century border."
Peña Nieto says it is a "mistake" to limit the U.S.-Mexico relationship to drugs and security concerns and has called for boosting economic ties as well.