President Francois Hollande held an emergency national defence council meeting after allegations by the online whistleblower WikiLeaks that America's National Security Agency (NSA) spied on three successive French presidents.
The meeting last night was "to evaluate the nature of the information published by the press ... and to draw useful conclusions", a presidential aide said.
WikiLeaks published documents it says show the NSA spied on top French government figures from at least 2006 until 2012.
"The top secret documents derive from directly targeted NSA surveillance of the communications of French Presidents Francois Hollande (2012"present), Nicolas Sarkozy (2007"2012), and Jacques Chirac (1995"2007), as well as French cabinet ministers and the French Ambassador to the United States," it said.
The revelation that the United States was spying on its close ally for political, economic and diplomatic intelligence is likely to cause a political storm in France, whose Parliament is finalising a new bill that would give French intelligence agencies sweeping new powers to monitor phone metadata and online activities.
The United States refused to confirm or deny the allegations. "We are not going to comment on specific intelligence allegations," the White House National Security Council said.
"As a general matter, we do not conduct any foreign intelligence surveillance activities unless there is a specific and validated national security purpose," it said.
Revelations that the NSA was allegedly eavesdropping on Angela Merkel's mobile phone sparked a political scandal in Germany in 2013 and led to the German Chancellor issuing a strong rebuke to the US.
"While the German disclosures focused on the isolated fact that senior officials were targeted by US intelligence, WikiLeaks' publication today provides much greater insight into US spying on its allies," WikiLeaks said.
The latest revelations consist of NSA intelligence summaries of conversations between top French officials on issues such as the global financial crisis, the Greek debt crisis, the leadership and future of the European Union, the website said.
Other issues included the relationship between Hollande's Socialist government and Merkel's Administration in Germany, French efforts to determine the make-up of the executive staff of the United Nations, and a dispute between the French and US governments over US spying on France.
The documents also detail mobile phone numbers of officials in the Elysee, including the president, the prime minister and other ministers.
All the documents were classified as "top secret" and were destined for NSA and other US intelligence chiefs, with just two of the five marked to be passed on to the "Five Eyes" - the intelligence partnership that includes the UK, Australia, Canada and New Zealand, French media said.