Brazil held counter-intelligence operations against diplomats from Iraq, Iran and Russia between 2003 and 2004, local daily Folha de Sao Paulo reported on Monday.
The daily said it had access to a document of the Brazilian Intelligence Agency (ABIN), which includes 10 secret operations monitoring foreign diplomats in their embassies and residencies.
The Brazilian Presidency's Institutional Security Cabinet (GSI), to which ABIN falls under, admitted that the surveillance operations were undertaken but said that they were held in accordance with Brazilian law.
On Monday, President Dilma Rousseff's office defended the practice, saying that these actions were held by the secret services on suspicion that other countries were conducting espionage operations against Brazil.
"These operations were held according to the Brazilian legislation to protect the national interests," Rousseff's office was quoted by the daily as saying.
In "Miucha" operation held in 2003, ABIN spied on three Russian diplomats, including former general consul in Rio de Janeiro, Anatoly Kashuba, the report said, adding that representatives of Rosoboronexport, the Russian weapon exporting agency, were also monitored.
In "Sha" operation, Brazilian intelligence kept tabs on activities of Iranian diplomats, including the then Iranian ambassador in Cuba, Seyed Davood Mohseni Salehi Monfared, during a visit to Brazil on April 9-14, 2004.
The daily said it had asked a Brazilian agent to examine the document and that the agent affirmed that probably the Iranians were spied as a request of secret services of another country, as part of the usual cooperation between intelligence agencies.
Rousseff's office said that GSI respects the constitutional rights of press freedom, but disclosure of secret classified reports is a felony and that the perpetrators will be prosecuted.