Maduro, in a speech broadcast Thursday night on state-run television, said suspected paramilitaries had been detained in a series of raids. On Friday, Vice President Jorge Arreaza said authorities, taking steps to prevent attempts to destabilize the country, had arrested two Colombians dressed in Venezuelan military outfits and seized equipment used with high-caliber military rifles.

"I can't divulge details because of an ongoing investigation," said Arreaza, who was accompanied at a news conference by Defense Minister Diego Molero,Air Max 90. "Fortunately, we have been able to neutralize this case of destabilization."

Nearly 19 million Venezuelans are eligible to vote in Sunday's poll, in which Maduro will square off against Miranda state Gov. Henrique Capriles. The winner will complete the term of , who died March 5 after designating Maduro as his political heir.

In his speech, Maduro, who is expected to win, said Capriles supporters were preparing to reject the election results.

"If they try to do it with a coup d'etat, we will make a revolution even deeper than what we have now," Maduro said. "We are prepared for what is and what could come."

Ramon Guillermo Aveledo, coordinator of the Capriles campaign, rejected the charges. "If they had the minimal proof, they would show it. They have nothing because it doesn't exist," Aveledo said Friday. "In military terms, this is a smoke screen."

Capriles has said the accusations were lies and made harsh claims of his own.

"We back no sort of destabilization," Capriles told thousands of supporters massed in the city of Barquisimeto, where he closed out his campaign Thursday. "When the polling places are closed, we must be present for the vote counting, because this group likes to pull tricks, and we can't let them rob our hopes and future."

El Salvadoran congressman Roberto D'Aubuisson, who was accused by Maduro last week of leading destabilization plans, appeared in Caracas on Friday to deny the charges. He told El Universal newspaper that he hoped Maduro would retract the charge.

The government this week ordered the country's borders with Colombia, Brazil and Guyana closed until Monday, a move officials said was a necessary security measure. Capriles called it "arbitrary."

Opposition figures believe the action was designed to deprive Capriles of votes from Venezuelans who work abroad.

Capriles ran unsuccessfully against Chavez in October. He agreed to run again after the National Electoral Council called for an election shortly after Chavez's death.

Kraul and Mogollon are special correspondents.