Felipe Calderon was sworn in as the president of Mexico Friday despite earlier brawls on the floor of the Congress between his supporters and those who believe the election was fraudulent.

Flanked by members of his ruling party and former president Vicente Fox, Calderon quickly swore to uphold the constitution.

The national anthem was then played, momentarily stilling whistles and shouting from opposition lawmakers who support his presidential opponent, Andres ManuelLopez Obrador.

"He did it! He did it!" chanted ruling party lawmakers.

Punches, chairs thrown

About an hour before Calderon was to take the oath of office, opposition politicians threw punches and chairs and tried to block the doors of the congressional chamber. Prime Minister Stephen Harper was to attend the ceremony.

The brawl was shown live on television across Mexico.

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Lawmakers scuffle as one uses a chair to try to block an access to Congress as opposition lawmakers try to block the arrival of president-elect Felipe Calderon on Friday. ((Dario Lopez-Mills/Associated Press))

Hours earlier, Calderonhad taken charge of Mexico's presidential residencein an unusual midnight ceremony.

"I have received the presidential offices from Fox, the start of the process of taking possession of the presidency," Calderon said in a live broadcast from the presidential residence of Los Pinos.

Calderon, 44,swore in some of his staff duringthe unprecedented ceremony.

"Nothing like this has happened in Mexico before, according to local media," said CBC correspondent Dave Taylor from Mexico City.

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Felipe Calderon, right, was sworn in as the president of Mexico Friday.

Supporters ofLopez Obrador maintain their candidate won the July vote. Lopez Obrador doesn't recognize Calderon's razor-thin victory andhas called forthousands of supportersto floodthe streets of Mexico City in protest.

Congress wasringed by police and presidential guards, as thousands of Lopez Obrador supporters marched through the city's streets following a rally at Constitution Plaza, where Lopez Obrador called for a peaceful protest.

Canadian officials have advised visitors to exercise "extreme caution" in the capital and avoid the demonstrations.

Harper was the first foreign leader to calland offer congratulations when Calderon was elected. He was invited to the inauguration when the new Mexican leader visited Ottawa in October, although Canadian leaders haven't attended in the past.

The prime minister will hold a bilateral meeting with Colombian President Alvaro Uribe Velez following the ceremony before returning to Ottawa.

Lopez Obrador'ssupporters occupied central Mexico City for months following the July election, demanding a full recount. In September, leftist lawmakers managed to block Fox from giving his state-of-the-nation speech in Congress by occupying the same dais.

With files from the Associated Press