The U.S. ambassador to France, Jane Hartley, has been summoned by Foreign Minister, Laurent Fabius, over revelations by WikiLeaks that the U.S. National Security Agency (NSA) spied on three French presidents, including incumbent, Francois Hollande.

Media reports said the spokeswoman for the U.S. embassy in Paris could not confirm or deny the invitation.

The French Foreign Ministry did not respond to immediate requests for confirmation.

Meanwhile, French President, Francois Hollande, has described NSA spying revelations as unacceptable.

Hollande said France `will not tolerate’ threats to its interest, in response to revelations that the (NSA) spied on top French authorities.

The reaction was contained in a statement issued by the Elysee Palace after an emergency cabinet meeting between the president and defence ministers.

Hollande said that reports, revealed by an online medium reflected `unacceptable facts that have already arisen between U.S. and France.’