The United States wiretapped France's current president Francois Hollande, as well as former presidents Jacques Chirac and Nicolas Sarkozy, according to WikiLeaks.

The revelations were first reported in French daily Liberation and on news website Mediapart, which said the National Security Agency spied on the presidents during a period between at least 2006 until May 2012, the month Mr Hollande took over from Mr Sarkozy.

WikiLeaks said the documents derived from directly targeted NSA surveillance of the communications of Mr Hollande (2012-present), Mr Sarkozy (2007-2012) and Mr Chirac (1995-2007), as well as French cabinet ministers and the French ambassador to the US.

Mr Hollande spoke by phone with US president Barack Obama, who gave fresh assurances that spying on European leaders had ended, while France's foreign minister summoned the US ambassador for a formal explanation.

"President Obama reiterated without ambiguity his firm commitment... to stop these practices that took place in the past and which were unacceptable between allies," Mr Hollande's office said in a statement after the call.

Mr Hollande earlier convened his top ministers and intelligence officials to discuss the revelations, with his office stating that France "will not tolerate any acts that threaten its security".

Confidential information tapped

The documents also contained the mobile phone numbers of numerous officials in the Elysee presidential palace, including the number of the president, WikiLeaks said.

They included summaries of conversations between French government officials on the global financial crisis, the Greek debt crisis, and the relationship between the Hollande administration and the German government of Angela Merkel.

The latest WikiLeaks drop comes just weeks after president Barack Obama signed into law a landmark legislation ending the US government's bulk telephone data dragnet.

Former NSA employee Edward Snowden created an uproar in Germany after he revealed that Washington had carried out large-scale electronic espionage in Germany and claimed the NSA had bugged Ms Merkel's phone.

"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.

This includes "the actual content of intelligence products deriving from the intercepts, showing how the US spies on the phone calls of French leaders and ministers for political, economic and diplomatic intelligence".

WikiLeaks founder Julian Assange said French citizens had a right to know their government was "subject to hostile surveillance from a supposed ally", and promised more "timely and important" revelations soon.

'Unacceptable methods' used, Sarkozy aide says

The most recent document was dated May 22, 2012, just days before Mr Hollande took office, and revealed the French leader "approved holding secret meetings in Paris to discuss the eurozone crisis, particularly the consequences of a Greek exit from the eurozone".

Another document dated 2008 was titled "Sarkozy sees himself as only one who can resolve world financial crisis", and, according to Wikileaks, "blamed many of the current economic problems on mistakes made by the US government, but believes that Washington is now heeding some of his advice".

Chirac's choice for appointments at the United Nations was the subject of a file dated 2006.

In that same document, then foreign minister Philippe Douste-Blazy was described as someone who has the "propensity ... for making ill-timed or inaccurate remarks".

The French ambassador to the US Gerard Araud appeared to downplay the revelations, stating on Twitter: "Every diplomat lives with the certainty that their communications are listened to, and not by just one country. Real world."

But an aide of Sarkozy blasted the alleged spying as "unacceptable methods as a general rule and more particularly between allies".

WikiLeaks said French readers could "expect more timely and important revelations in the near future".

Last week, WikiLeaks published more than 60,000 diplomatic cables from Saudi Arabia and said on its website it would release half a million more in the coming weeks.

AFP/Reuters