Brazil, which hotly denounced US surveillance of its leaders, itself spied on US officials as well as on Russia, Iran and Iraq a decade ago, the Folha de Sao Paulo newspaper reported on Monday.
The paper indicated it had access to a document from the Brazilian Intelligence Agency, ABIN, describing surveillance operations from 2003 and 2004, during the first mandate of former president Luiz Inacio Lula da Silva.
Brazil kept tabs on rooms rented by the US embassy in Brasilia, which ABIN believed acted as a hi-tech base for espionage operations, the document showed.
ABIN concluded that the rooms housed computers and communications devices. Responding to Folha, the US embassy denied espionage activities took place in the building, saying only day-to-day equipment, such as walkie-talkies, were stored there.
Brasilia also spied on Russian military personnel involved in negotiations for military equipment, as well as on Moscow's former consul general in Rio, Anatoly Kashuba.
And ABIN monitored Iran's then-ambassador to Cuba, Seyed Davood Mohseni Salehi Monfared, when he visited Brazil between April 9-14, 2004, and spied on Iraq's embassy, shortly after the 2003 US-led invasion of the country.
The Brazilian surveillance was on a far more modest scale than that carried out by the US National Security Agency (NSA), which monitored millions of high-level Brazilian communications, according to documents leaked by fugitive former NSA contractor Edward Snowden.
The Snowden documents show NSA monitoring stretched all the way up to the phone calls of Brazilian President Dilma Rousseff as well as at state oil giant Petrobras.
Rousseff condemned the NSA monitoring in an address last month to the United Nations and also broke off a scheduled visit to Washington in protest. Brazil says it hopes to interview Snowden, currently in exile in Russia.
On Monday, Rousseff's office responded to Folha's report by stating the surveillance in question comprised "counter-intelligence operations" undertaken a decade ago.
"The operations in question (took place) in accordance with Brazilian legislation pertaining to the protection of the national interest.
"As Folha preferred not to send copies of the documents obtained, the Institutional Security Cabinet (GSI) could not verify their authenticity," the presidential office stated, adding publication of classified documents was a criminal offense and would be punished.
Folha said it had interviewed several former intelligence officials, agents and military in order to confirm the authenticity of the document in its possession.