U.S. allegedly accessed ex-Mexican president's email

The United States National Security Agency (NSA) is reported to have accessed emails of former Mexican President Felipe Calderon.

According to Germany's Der Spiegel daily, documents from NSA leaker Edward Snowden described an operation called "Flat Liquid" which allegedly accessed Calderon's domain, and claimed that the information was also used by members of his cabinet.

President Enrique Pena Nieto has demanded an investigation into the matter, calling it an illegal act, Fox News reports.

Earlier, a document indicated that the NSA had read Nieto's emails, before he was elected.