Mexico City - Conservative Felipe Calderon was sworn in as Mexico's president on Friday, despite threats from opposition lawmakers that looked likely to derail the ceremony and a fight that broke out just hours before the inauguration was set to begin.
The brief ceremony in the main chamber of the lower house of Congress took place amid heckling by leftist legislators, who had attempted to prevent or disrupt the inauguration. Calderon did not deliver the speech that is traditionally made by new presidents.
Lawmakers from both Calderon's party and Leftist former presidential candidate Andres Manuel Lopez Obrador's Party of the Democratic Revolution (PRD) had occupied the podium of the lower- house of Congress for much of the week amid threats that the inauguration ceremony would be disrupted by opposition supporters.
Lopez Obrador has claimed fraud occurred in July presidential elections which Calderon won by only 0.56 percentage points. Since the election, Lopez Obrador's supporters have vowed to prevent or disrupt Calderon's inauguration and presidency.
A fight broke out at 8 am (1400 GMT) Friday when Santiago Creel, the Senate leader of Calderon's National Action Party (PAN), arrived in Congress. A self-imposed truce between legislators to avoid violence expired at that time.
The early fight included punching, pushing and the throwing of chairs. Rival factions shouted 'No to Calderon' and 'No to usurpation,' while Calderon's party yelled 'Calderon, Calderon' and 'Reconciliation.'
Fisticuffs first broke out Tuesday in an atmosphere of tension that had appeared to suggest that the inauguration ceremony could turn violent.
Earlier Friday, Calderon moved into the presidential palace in Mexico City and issued his first presidential message at midnight.
Raising his right arm, Calderon took his oath before Congress as prescribed by the Constitution. He received the presidential sash from outgoing President Vicente Fox amid applause from ruling-party legislators and whistling from opponents, and sang the country's national anthem.
'We could make it, we could make it,' shouted lawmakers of Calderon's and Fox's National Action Party (PAN), in a ceremony that - despite lasting only very few minutes - frustrated the attempts of their leftist peers to prevent the transfer of power.
After taking his oath, Calderon left Congress and moved into a nearby secured area. The area, comprising several blocks around the National Auditorium in Mexico City, has been turned into a fortress, and access is strictly limited to those who have specific credentials.
Beginning at noon (1800 GMT) Calderon is expected to attend an open-air rally at the auditorium, which holds 10,000 people. He is set to address members of his own party.
Later, he is to attend a military ceremony at the nearby Campo Marte and to host a lunch for legislators, governors and special guests at the National Museum of Anthropology and History.
In the evening, he is expected to host a state dinner at the Chapultepec Castle for heads of state attending his inauguration.
All foreign guests - including former US president George Bush and Spanish crown prince Felipe de Borbon - and Fox are staying in the secured area on both sides of the central Reforma Avenue.
Lopez Obrador changed earlier plans to march on Congress and instead decided to march 'peacefully' through the centre of Mexico City to avoid clashes with police.
The demonstration is set to get as far as the entry of the Chapultepec Park, which is also the entrance to the secure area.
© 2006 dpa - Deutsche Presse-Agentur