Venezuela's ruling party accused opposition members and the US ambassador to Colombia on Wednesday of plotting a coup and the assassination of President Nicolas Maduro.
The accusations came as the US House of Representatives voted overwhelmingly to impose sanctions on Venezuelan officials responsible for a crackdown on anti-government protests that have left at least 42 people dead.
Surrounded by socialist party leaders, Jorge Rodriguez, the mayor of the Caracas municipality of Libertador, said US ambassador Kevin Whitaker acted as a coordinator "in a coup in collusion with Venezuelan politicians and civilians."
Rodriguez showed reporters emails written by former opposition lawmaker Maria Corina Machado and other government critics in which they allegedly discuss how to heat up a political crisis to oust Maduro.
Rodriguez read an email in which Machado allegedly told former presidential candidate Diego Arria of the need to "step up efforts" and obtain financial help to "annihilate Maduro."
The mayor said the three-month-old anti-government protests that have rocked Venezuela are "a phase" in an elaborate plot by the far-right, which he said planned street barricades, a military coup and the assassination of Maduro.
Machado, who was ousted from the legislature by Maduro's United Socialist Party of Venezuela (PSUV) in March, said the email addresses belonged to her but that the messages shown by the PSUV were fake.
She denied communicating with Whitaker via email, though she admitted having met with him, as well as with a senior US State Department official and the foreign ministers of Argentina, Brazil, Mexico, Chile and Canada.
She said she would lodge a complaint before a Venezuelan court on Thursday.
The Venezuelan government has regularly accused the United States and the opposition of plotting to destabilize Maduro's administration ever since he succeeded late leader Hugo Chavez in elections last year.