No independent official confirmation of reports was immediately available but the Brazilian Veja magazine cited police and security forces that were alerted to the activities of at least 20 high-ranking operatives of three organizations -- al-Qaida, Hamas and Hezbollah.
Reports of possible Middle Eastern terror links with the area first emerged after the Sept. 11, 2001, attacks on the United States, re-emerged last year but were dismissed amid concerns the allegations would alienate and anger local communities of Arab descent, most of them Christian.
More recent reports cited activities by al-Qaida and Iran-linked groups that likely used connections among non-Christian Middle Eastern communities.
Community leaders countered previous allegations as inspired propaganda which, they warned, could damage inter-faith and inter-racial relations.
The reports also cited large quantities of cash changing hands and deals with arms suppliers, several of which are linked to supplies of weapons manufactured locally in Latin America.
Analysts said the reports still need to be treated with caution. A spate of recognitions by regional governments of a Palestinian state in borders before the 1967 war gave rise to speculation the Latin American states could be tilting toward the Palestinian position on ways of resolving the Arab-Israeli disputes.
The wave of recognitions hasn't affected the current Middle East stalemate, though it has raised the stakes in the diplomatic and political jockeying for influence between Israel and the Arab-Palestinian side.
The renewed allegations of terror links in the region again shifted the spotlight on Arab communities in the area. Brazil earlier discounted reports of suspect activities, pointing out that large money transfers between the local Arab communities and the Middle East was a normal activity that had gone on for years.
Veja said the intelligence agencies' interest was focused on Mohsen Rabbani, a former Iranian cultural attache at the Iranian Embassy in Buenos Aires, in connection with 1992 and 1994 incidents targeting Argentina's Jewish communities.
Veja said Brazilian intelligence had tracked Rabbani's alleged role in recent travel to a meeting in Iran by more than 20 young men from the Sao Paulo area.
The magazine said other individuals of Arab descent were suspected of activities considered inappropriate and claimed that both the Lebanese Hezbollah organization and Palestinian group Hamas had set up operations in the border region.
The so-called Triple Frontier has long held reputation as South America's busiest contraband and smuggling hub with unbridled trade in arms, bootleg liquor, drugs and pirated software.
The area came under close surveillance by U.S., other international and regional intelligence agencies after 9/11.