MEXICO CITY -- President Ernesto Zedillo is facing a critical test of his promised new era of federalism and reform after ruling party leaders in the troubled southern state of Tabasco seized an international airport, a major radio station and most roads leading to the state's capital.


The open rebellion against federal authority was spurred by rumors that Zedillo and national party leaders were negotiating the resignation of the state's recently inaugurated governor to defuse a post-election conflict in the oil-rich state.


Thousands of Institutional Revolutionary Party (PRI) loyalists, many armed with torches and wooden clubs, swarmed the capital Villahermosa to resist Governor Jorge Madrazo Pintado's dismissal. The protests began Wednesday, when the crowds paralyzed the state's government, more than half the state's businesses and temporarily closed the airport.


In defiant radio broadcasts, state PRI leaders also threatened to resign en masse from the party that has ruled Mexico for the past 65 years if its national leadership gives in to opposition demands that Madrazo resign in exchange for peace.


Compounding the chaos were continuing protests by the state's opposition Democratic Revolutionary Party (PRD), which claims Madrazo won gubernatorial elections last November through ruling-party fraud. Opposition supporters have blockaded key oil installations and the governor's office since Madrazo's Dec. 31 inauguration.


Thursday's dueling demonstrations resulted in at least one injury when an opposition legislator was beaten by ruling party protesters.


Since its creation, the monolithic PRI has been ruled with the strict authoritarian control of the nation's president.


Thursday's uprising fueled speculation that Zedillo's bold policy to separate the party and government was already weakening the PRI from within, and it added to Zedillo's image problems amid a continuing economic emergency fueled in part by unrest in the south.