The Brazilian army has been accused of giving Amazon Indians guerrilla training after a newspaper published leaked photographs depicting troops apparently showing tribesmen how to use assault rifles.
The army denied there was anything irregular about its actions, saying the participation of Indians in special forces training sessions was routine in the states of Rio de Janeiro, Goias and Amazonas.
In a written statement, the army said: "This kind of activity is based on the practice of 40 years of work of the special forces together with indigenous communities or [their] descendants."
But representatives of Brazil's Foundation for the Protection of Indians (Funai) have called for an immediate investigation. Funai's chief prosecutor, Luiz Villares, said his organization had not authorized the use of Indians in army training sessions.
"We will ask the federal public prosecutor to investigate [and] I will send a request for an explanation to the army, explaining that they cannot do this and that they must stop," he told the Rio newspaper Extra.
One of the pictures published on Sunday shows a line of crouching indigenous women brandishing automatic rifles. Another features an Indian man, in black flip-flops and orange shorts, aiming an assault rifle under the gaze of a uniformed soldier.
There were contradictory reports as to when the pictures were taken and what the Indians were doing.
According to army officials in Brasilia, the photographs were taken in the Amazon region in the 1980s. But an arms expert consulted by the newspaper said one of the weapons seen in the pictures was a Colt M4 rifle, which has been employed by Brazil's army only since 2004.
There were also conflicting accounts of what the Indians were doing in the photos.
Jose Alvez Firmino, the president of the National Federation of Military Soldiers, said the pictures showed "guerrilla training."
But army officials said the Indians, who they claimed were volunteers, were being used to train soldiers for "war scenarios." The army's statement also said those pictured were actually descendants of Indians.
"Almost all of the communities in the interior of the Amazon are [made up] of descendants of Indians, which could probably confuse a careless observer," it said.
Villares rejected this as a justification, saying: "The use of Indians does not have the authorization of Funai. This applies to descendants as well as Indians."
Priscila Carvalho of Brazil's Indigenous Missionary Council said the Indians may have been used because of their knowledge of the sprawling rainforest.
"We know that this is going on in various places and imagine that it has to do with them having a greater knowledge of the region," she said.
The revelations came as Amnesty International accused the Brazilian government of failing to protect the country's indigenous population from violence and poverty.