France and Mexico have angrily demanded prompt explanations from the United States following "shocking" new spying allegations leaked by former US security contractor Edward Snowden.
The reports published in French daily Le Monde and German weekly Der Spiegel reveal that the US National Security Agency secretly monitored tens of millions of phone calls in France and hacked into former Mexican President Felipe Calderon's email account.
They come on top of revelations also leaked by Snowden and published in June that the US had a vast, secret programme called PRISM to monitor Internet users.
French Foreign Minister Laurent Fabius, on a trip to Luxembourg for a meeting with his EU counterparts, said the US ambassador had "immediately" been summoned to his ministry for a meeting Monday morning.
"These kinds of practices between partners that harm privacy are totally unacceptable. We have to rapidly make sure that they are no longer implemented in any circumstance," he told reporters.
French Interior Minister Manuel Valls, meanwhile, described the revelations as "shocking", in an interview with Europe 1 radio.
The spy agency monitored 70.3 million phone calls in France over a 30-day period between December 10 and January 8 this year, Le Monde reported in its online version, citing documents from Snowden.
According to the paper, the NSA automatically picked up communications from certain phone numbers in France and recorded certain text messages under a programme code-named "US-985D."
Le Monde said the documents gave grounds to believe that the NSA targeted not only people suspected of being involved in terrorism but also high-profile individuals from the world of business or politics.
Valls said France would demand "precise explanations by US authorities in the coming hours."
US authorities declined comment to the French daily on the "classified" documents.
The Le Monde article followed revelations by Der Spiegel -- also based on documents provided by Snowden -- that US agents had hacked into the Mexican presidency's network, gaining access to Calderon's account.
According to the report, the NSA said this contained "diplomatic, economic and leadership communications which continue to provide insight into Mexico's political system and internal stability."
The agency reportedly said the president's office was now "a lucrative source."
Mexican authorities said they would be seeking answers from US officials "as soon as possible" following the allegations.
"The Mexican government reiterates its categorical condemnation of the violation of privacy of institutional communications and Mexican citizens," Mexico's foreign ministry said in a statement Sunday.
"This practice is unacceptable, illegitimate and contrary to Mexican law and international law," the statement read.
Snowden, who has taken refuge in Russia, is wanted in the United States for espionage and other charges after leaking details of the NSA's worldwide snooping activities that were published in June.
The fugitive had been in hiding in Hong Kong since May and flew to Moscow on June 23, where he stayed in the transit area for more than a month before being given temporary asylum and leaving the airport for a safe location.
US President Barack Obama has since proposed reforms of US surveillance programmes in the wake of the furore.