CARACAS, Venezuela — President Chavez has ordered an investigation into a purported plot to assassinate him and topple his government.

Mr. Chavez said late yesterday that his government eavesdropped on a group of conspirators who considered blowing up the presidential jet or bombing the presidential palace.

Mr. Chavez ordered his defense minister to investigate the alleged conspiracy involving a vice admiral from his inner circle and other former military officers.

“Evidently, there’s a conspiracy,” Mr. Chavez said on state television, according to a government statement. “We’ve been following this for some time.”

As of this morning, no one was detained in the case, Justice Minister Tarek El Aissami said.

A Chavez ally, Mario Silva, who hosts a program on state television, played a recording late yesterday of a purported phone conversation in which alleged conspirators discussed plans to overthrow Mr. Chavez.

Mr. Silva said Vice Admiral Carlos Millan was among them, along with two other ex-officers from the National Guard and the air force.

In the recording aired, a voice identified as an ex-officer said “we’re going to take” the presidential palace.

Mr. Chavez survived a 2002 failed coup and often has accused opponents of trying to oust him again.

The former paratroop commander said the conspirators have been “looking for ground-to-air missiles … to try to blow up the presidential plane … or bomb the (presidential) palace with a plane.”

Mr. Chavez called his opponents “little Yankees” and said they are following orders from Washington.

He has repeatedly accused President Bush’s administration of backing coup-plots. American officials deny it.