From its neighbor Mexico down to Argentina, Latin American nations are demanding answers from the United States after a report of vast US spying on close allies and leftist critics alike.
Governments voiced a mix of outrage and concern after the Brazilian daily O Globo, citing documents leaked by fugitive former US intelligence contractor Edward Snowden, said several nations were targets of US electronic surveillance.
The snooping included lifting data on leftist Venezuela's oil and military purchases and Mexico's drug war and energy sector as well as mapping the movements of a Marxist guerrilla group in Colombia, the newspaper said.
Mexican President Enrique Pena Nieto said Wednesday his government had asked for "an explanation to clear up" the spying claims and that if they turn out to be true, "it would be completely unacceptable."
Pena Nieto, however, said the two allies still maintained relations of "respect and cordiality."
The Mexican daily Excelsior reported Wednesday that Pena Nieto's predecessor had allowed the United States to install a system to intercept phone calls and Internet chatter.
The Mexican attorney general's office opened an investigation to determine whether a crime was committed.
Mexico and the United States have worked closely in the battle against drug trafficking in recent years, with the US government earmarking $1.9 billion in law enforcement training and equipment.
The reported spying on the energy sector comes as Pena Nieto, who took office in December, mulls a reform aimed at attracting more private investment in the state-run oil monopoly Pemex.
O Globo said other countries targeted by the National Security Agency were Argentina, Ecuador, Panama, Costa Rica, Nicaragua, Honduras, Paraguay, Chile, Peru and El Salvador.
"It sends chills up my spine when we learn that they are spying on us through their intelligence services in Brazil," Argentine President Cristina Kirchner said, referring to another Globo report that the United States maintained a satellite spy base in Brasilia at least until 2002.
The issue will be on the agenda of Friday's summit of the Mercosur trade bloc, which includes Brazil, Argentina, Uruguay and Venezuela. The leaders of Bolivia and Honduras were also invited to the talks in Montevideo.
"The Mercosur meeting is an opportunity to take a common stand. Any attack on the sovereignty of one country must be answered with great firmness, because if we lower our heads, they will walk all over us," warned Brazil's presidential chief of staff Gilberto Carvalho.
President Dilma Rousseff has ordered an investigation into the report of electronic spying on Brazilian citizens and companies.
Colombia, the top US ally in the region which has received billions of dollars in US military aid to combat drug trafficking and the leftist rebels, voiced concern and said it would seek answers from the United States.
A foreign ministry statement late Tuesday said that Colombia rejects "acts of espionage that violate people's right to privacy and international conventions on telecommunications."
The US ambassador to Colombia, Michael McKinley, said he understood "expressions of concern" and that the United States had an obligation to respond through diplomatic channels to its partners.
US State Department spokeswoman Jen Psaki said that any answers to requests from countries such as Colombia would remain private.
"We have a range of diplomatic conversations with a broad number of countries, and as any allegations surface, we're happy to have those, but we keep those private for obvious reasons," Psaki said.
In Chile, the foreign ministry said it "firmly condemns espionage, whatever its origin, nature and objective."
El Salvador's deputy development minister, Jaime Miranda said, his government was checking the veracity of the claims, which would "clash with the principle of sovereignty and violate Salvadorans' right to privacy."
The outrage comes as Snowden, who is believed to be holed up in Moscow's international airport, is considering taking asylum in Latin America after the leftist leaders of Venezuela, Bolivia and Nicaragua offered to take in the 30-year-old fugitive.