(CNN) -- Venezuela's interim leader has upped the ante in his accusations about U.S. plots to destabilize his country, calling on President Barack Obama to investigate.
"Factors in the Pentagon and the CIA" are conspiring as elections approach in the South American country, interim President Nicolas Maduro said this week.
"We want to say to President Barack Obama, stop this madness," Maduro said during a campaign planning meeting broadcast Monday on state-run VTV.
The United States has been denying a steady stream of accusations from the acting leader ever since the day he announced President Hugo Chavez's death. Monday was no exception.
"Let me say it here extremely clearly, looking right at you," State Department spokeswoman Victorial Nuland told reporters. "The United States categorically rejects allegations of any U.S. government involvement in any plots to destabilize the Venezuelan government or to harm anyone in Venezuela."
Hours before he announced that Chavez had died on March 5, Maduro said that a U.S. Air Force attache had been expelled from Venezuela and accused him of seeking military support for a plot against Chavez.
Chavez's criticisms of U.S. imperialism were a hallmark of his presidency and played well with his supporters.
And some analysts say it's no surprise that the accusations have escalated with Maduro on the ticket to replace Chavez in presidential elections April 14.
Maduro, meanwhile, has remained firm in his claims.
"I am saying the absolute truth," Maduro said, "because we have the testimonies and direct, first-hand information."
Last week Maduro announced that planning was in the works for a commission of "the world's best scientists" to investigate whether Chavez, who died after battling cancer, had been poisoned. Maduro stressed that he wasn't accusing the United States, but he implied that the United States could have been behind such an attack on Chavez.
In the 1940s and 1950s, the United States and other countries had "scientific laboratories testing how to cause cancer," Maduro said. "Seventy years have passed. These kinds of laboratories of evil and death have not advanced?"
Also last week, he accused Otto Reich and Roger Noriega -- two fierce critics of Chavez's government who once worked for the U.S. State Department -- of plotting to assassinate Henrique Capriles Radonski, the opposition candidate for Venezuela's presidency.
Reich and Noriega both denied the accusations and warned that it could be a sign that Venezuela's government was involved in a plot of its own against the opposition candidate.
"These charges are so removed from reality that they may well be a smoke screen behind which the Venezuelan government is planning to eliminate Capriles," Reich said in a Twitter post Sunday.
Noriega said Monday that Cuban officials could be behind the accusations, which he described as "no laughing matter."
"Of course, this is a baseless, malicious lie, but it should not be dismissed as a cynical campaign tactic," Noriega wrote in an online post.
Maduro has said his government was offering security for Capriles.
"This candidate knows that he has all the guarantees to conduct his campaign in liberty," Maduro said, "and we are going to avoid any craziness against him."