Chavez, addressing 10 South American leaders gathered at a summit, gave no additional details. The accusation came less than two weeks after Chavez announced he would nationalize CA Nacional Telefonos de Venezuela, known as CANTV.
"Well I just announced the recovery of the state property of the Venezuelan telephone company," Chavez said. "Who controls it? North American capital. And they've used the Venezuelan telephone company to record the president of the Republic. Brother, it's the empire!"
Though Chavez referred to "North American capital" as being responsible for using the company to spy, he did not mention the United States by name. But Chavez frequently uses the term "empire" to refer to the U.S. government.
CANTV is Venezuela's largest publicly traded company, and its largest stockholder is New York-based Verizon Communications Inc.
Chavez has had tense relations with the United States since he became president eight years ago, and frequently accuses U.S. President George W. Bush of trying to overthrow him, claims that are fiercely denied by American officials, reports AP.
U.S. Embassy spokesman Brian Penn declined to comment on the accusation about CANTV.
The choice of the city of Helsinki is not incidental as the capital of Finland had hosted US-Soviet negotiations on the limitation of nuclear stockpiles in 1969