Braslia - Venezuela's fugitive former top prosecutor resurfaced in Brazil on Wednesday claiming to possess "a lot" of proof of President Nicolas Maduro's corruption and warning that her life remains in danger.Days after a dramatic escape from chaotic Venezuela, Luisa Ortega, 59, turned up the heat on Maduro, who has asked Interpol to issue a "red notice" warrant for the arrest of his critic.Ortega - speaking at a crime-fighting conference in the Brazilian capital with representatives from the Latin American regional trading alliance Mercosur - said Maduro enriched himself in a massive corruption scheme uncovered at Brazilian construction conglomerate Odebrecht."I have a lot of proof, concretely in the Odebrecht case, which implicates many high-ranking Venezuelans, starting with the president of the republic," she said."The rule of law has died" under Maduro, she said, suggesting the country has become a criminal haven where evidence in organised crime cases tends to "disappear"."There are many in Venezuela who have an interest in stopping investigations of corruption cases or cases related to drug trafficking or terrorism," she said.READ: Pence vows US will not allow 'collapse of Venezuela''Death threats'The move came as US Vice President Mike Pence vowed Washington would not allow "the collapse of Venezuela", amid a political crisis triggered by Maduro's decision in July to set up a new constitutional body, in a move widely seen as a power grab.Ortega, who fled to Colombia from Venezuela with her husband German Ferrer on August 18, said she was still in danger."I have received threats that there may be an attempt against my life and I hold the Venezuelan government responsible if this happens," she said at the conference, which she attended after flying to Brasilia from Panama.Brazil's prosecutor general said in a statement that he had personally invited Ortega, adding to the intrigue since she was fired by Venezuela's socialist president this month and charged with misconduct.The prosecutor appointed under Maduro to take Ortega's place dismissed her allegations, saying: "They have no legal validity."They would have validity if she had presented these supposed proofs before the judicial system," said the chief prosecutor, Tarek William Saab, in Caracas.Saab described Ortega's statements as "libellous propaganda" and suggested there was a hidden agenda behind her traveling in exile. "We should see who is supporting these trips."On Tuesday, Maduro said Ortega and Ferrer had committed "serious crimes" and should be apprehended. Ferrer is accused by Maduro's government of corruption and extortion.Political unrestHowever, neighbouring Colombia and Brazil have come to Ortega's defence and firmly condemn Maduro's handling of violent political unrest and economic collapse in his oil-rich country.Venezuela has been suspended indefinitely from the Mercosur group.A loyalist of late socialist president Hugo Chavez, Ortega broke ranks with his successor Maduro to become his most high-ranking critic within the government as international pressure on the president mounted.In July, Maduro set up a constituent assembly packed with his allies, which a few days later removed Ortega from her post.She has hit back since fleeing, using her growing international platform to accuse Maduro and his close allies in the Odebrecht scandal, which involved enormous quantities of bribes paid to politicians around the region and in Brazil to win contracts."We have all the elements that incriminate not only the president, but his close advisors," she said on Wednesday, fingering Diosdado Cabello, a prominent ruling party member."In the Odebrecht case, we have discovered that they deposited $100m for Diosdado Cabello to a Spanish company called TSE Arietis, whose owners are his cousins," she said.Cabello later denied the charges and ridiculed Ortega on his weekly TV show.Maduro was elected in 2013 after the death of his late mentor Chavez.Venezuela has since descended into chaos that has raised fears for regional stability.The fall in world prices for its oil exports has left it short of dollars for vital imports.Maduro's critics accuse him of clinging to power by hijacking state institutions amid shortages of food and medicine.Clashes between protesters and police this year have left 125 people dead, according to prosecutors.