Enrique Peña Nieto was inaugurated Saturday as Mexico's president, returning the Institutional Revolutionary Party, or PRI, to power after a 12-year hiatus.
He was sworn in shortly before noon during a joint session of Congress preceded by protests from opposition lawmakers.
Outgoing President Felipe Calderon kissed the presidential sash before handing it over to his successor amid cries by legislators in favor and against Peña Nieto, a telegenic former governor of the central state of Mexico.
Soon after taking office, the new president announced 13 decisions by his government including the creation of a national crime-prevention program that will combat the nation's incessant violence with comprehensive measures.
"I'm convinced that crime is not defeated by force," Peña Nieto said in his first address to the nation.
The crime-prevention program ranks No. 1 among his most immediate objectives, which also include a series of legal and administrative reforms to combat poverty while promoting investment and controlling government spending.
"Mexico demands to live in peace," Peña Nieto said.
In the chamber of the lower house, where the ceremony was held, a large banner was carried by opposition lawmakers with crosses of mourning that said "Imposition accomplished, Mexico in mourning," referring to the left's claims that Peña Nieto's victory in the July election was due to widespread electoral fraud.
Leftist lawmakers carried posters with such slogans as "From a failed state with Calderon to a state sold out under his successor" and "president of violence," an allusion to the outgoing head of state.
Some 60,000 people were killed in drug-related violence during the six-year presidency of Calderon, who militarized the struggle against Mexico's violent, well-funded cartels by deploying tens of thousands of army soldiers to drug-war hotspots.
But there were also small signs carried by PRI lawmakers saying "Mexico unites us."
The ceremony took place after more than an hour's delay, while outside the legislative chamber, guarded by hundreds of police, there were clashes between protesters and security agents that left at least one person seriously injured.
Despite the initial protests and banners in the legislature, the session differed significantly from the rowdy inauguration of Calderon on Dec. 1, 2006.
On that occasion, Calderon and his predecessor, Vicente Fox, both members of the National Action Party, or PAN, had to enter the government building by side doors, amid attempts by opposition lawmakers to take over the lower house of Congress.
Calderon won the 2006 election by the narrowest margin in Mexican history over leftist candidate Andres Manuel Lopez Obrador, who was also the runner-up to Peña Nieto.
Lopez Obrador and his leftist PRD party denounced Calderon as a "spurious president" whose ostensible victory was the result of machinations by big business and Fox's administration.
The PRI, which governed Mexico from 1929 to 2000, lost the 2000 presidential election to the PAN and finished third in 2006.
During its 71-year reign - described by Peruvian Nobel literature laureate Mario Vargas Llosa as the "perfect dictatorship" - the PRI relied mainly on patronage and control of organized labor and the mass media, though it was not above resorting to outright vote-rigging and even violence. EFE