(CNN) -- Mexican President-elect Enrique Peña Nieto was sworn in before Congress on Saturday, after he assumed control of the armed forces and national security in a symbolic ceremony held earlier.
Exactly as scheduled, at 12:01 a.m. local time, President Felipe Calderon and Peña Nieto walked down the escalators to a patio in the National Palace.
In a ceremony lasting about five minutes, Calderon received the national flag from a military school cadet and immediately handed it to Peña Nieto. The act symbolized the transfer of command of the security forces.
Afterward, both men greeted members of the new Cabinet, then the outgoing Cabinet members.
Minutes later, in a separate ceremony, Peña Nieto conducted the oath of office of the new Security Cabinet, comprised of Miguel Angel Osorio Chong as the head of the Ministry of the Interior, Salvador Cienfuegos Zepeda as head of the Ministry of National Defense and Vidal Soberon Sanz as Secretary of the Navy.
Peña Nieto, who heads the Institutional Revolutionary Party, known as the PRI, said the new government had taken office "from the first minute of this day."
"A governmental transition has been completed in an orderly, legal and transparent fashion," he said.
"This process has helped to preserve the political stability, economic and social development of the nation. Mexico has shown democratic maturity and institutional strength," he said. "In accordance with Article 83 of the constitution, today I begin to exercise the honorable position of president of the United States of Mexico."
Peña Nieto and Calderon took to social media to commemorate the transition.
"My term ends, but not my commitment to Mexico, which I will continue fighting until the last of my days," Calderon tweeted.
Another of his tweets read: "The handover of the national flag for the change of guard from the president to the president-elect symbolizes the transfer of command."
Peña Nieto tweeted: "Starting today, I begin to occupy the post of Constitutional President of the United Mexican States. I am confident in my team and I recognize their track record, which supports its commitment to Mexico."