More than half of the women interviewed for an Oxfam report in 2009 had been forced to leave their homes since 2003, either because of violence or to seek employment.
The Brazilian President Luiz Inacio Lula da Silva has blamed the country's intelligence services for failing to warn him of the uprising by right-wing extremists earlier this month.
In mid-March Alphamin, a firm that operates a large mine in the Democratic Republic of Congo (DRC), suspended production because of attacks by insurgents.