The spying spanned 2006 to 2012, French newspaper Liberation and the Mediapart website, said on Tuesday, quoting documents classed as "Top Secret" which include five reports from the US National Security Agency based on intercepted communications.
The most recent document is dated May 22, 2012, just days before Hollande took office, and reveals that 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".
Hollande called a meeting of his defence council to discuss the reports on Wednesday.
Ever since documents leaked by former NSA contractor Edward Snowden showed in 2013 that the NSA had been eavesdropping on the mobile phone of German Chancellor Angela Merkel, it had been understood that the US had been using the digital spying agency to intercept the conversations of allied politicians.
Still, the new revelations are bound to cause diplomatic embarrassment for the Americans, even though allies have been spying on allies for thousands of years.
Hollande said last year that he discussed his concerns about NSA surveillance with President Barack Obama during a visit to the US, and they patched up their differences.
Spy scheme reviewed
After the Merkel disclosures, Obama ordered a review of NSA spying on allies, after officials suggested that senor White House officials had not approved many operations that were largely on auto-pilot. After the review, American officials said Obama had ordered a halt to spying on the leaders of allied countries, if not their aides.
Neither Hollande's office nor Washington would comment on the new leaks. Contacted Tuesday by AFP, Hollande's aide said: "We will see what it is about."
US State Department spokesman John Kirby meanwhile said: "We do not comment on the veracity or content of leaked documents".
WikiLeaks spokesman Kristinn Hrafnsson said he was confident the documents were authentic, noting that WikiLeaks previous mass disclosures have proven to be accurate.