French fury about a report that the U.S. spied on millions of phone calls made by French citizens continued to simmer Tuesday, with Foreign Minister Laurent Fabius using a meeting with U.S. Secretary of State John Kerry to issue a fresh admonishment.

Fabius and Kerry had breakfast together in Paris before both left for London, where they attended a meeting of the pro-opposition Friends of Syria group. In a statement, the French Foreign Ministry said Fabius had asked Kerry to explain the "unacceptable spying practices between partners, which must stop."

The meeting came hours after a telephone call between Presidents Francois Hollande and Barack Obama, in which Hollande also condemned the spying as "unacceptable between friends and allies."

Le Monde reported Monday that documents leaked earlier this year by whistleblower Edward Snowden showed the U.S. National Security Agency (NSA) collected 70.3 million recordings of French phone data over a 30-day period in December 2012 and January 2013.

France reacted with predictable indignation, summoning the U.S. ambassador.

The spying, which makes France the third most eavesdropped-on U.S. ally in Europe, after Germany and Britain, targeted people in business, politics and the civil service as well as terrorism suspects, Le Monde said.

The paper followed up Tuesday with a report about the surveillance of French diplomatic missions in Washington and New York using bugs remotely implanted inside diplomats' computers, among other devices.

Most of that information had already been revealed by German news magazine Der Spiegel in September.

In his call with Hollande, Obama acknowledged that the revelations raised "legitimate questions" for U.S. allies, the White House said.

Kerry sought to downplay the importance of the report, telling reporters in Paris Monday that "lots of countries are engaged in the activity of trying to protect their citizens and the world."

The affair threatens to strain relations between the U.S. and France, which Kerry called "one of our oldest allies."

France is still smarting at having gone out on a limb to support the U.S. when it was threatening missile strikes against Syria only to be shunted aside in the final negotiations with Russia on a chemical disarmament plan.

The French Communist Party on Tuesday called on the Socialist government to counter the "American aggression against our country" by withdrawing from NATO and severing military and police cooperation with the U.S.

The tensions dominated headlines. "The Spy Who Loved Us," read the front-page headline in the free Metro News daily - a play on the title of the 1977 James Bond film, The Spy Who Loved Me.

In an editorial entitled "Fighting Big Brother" Le Monde drew parallels with another film. "The systematic intrusion into private live is the stuff of totalitarian systems, as the (2006) film The Lives of Others, which described the Stasi apparatus in East Germany, reminded us," the paper said.

The past six months has seen a steady stream of disclosures about U.S. spying programs, based on secret documents leaked by exiled former NSA contractor Snowden. The documents show the U.S. delving deep into the communications of foreign governments and citizens, whether friends, rivals or foes of the U.S.

The U.S. response has been to argue that all countries conduct spying operations.

In July, Le Monde reported that France's external intelligence agency ran its own spying program targeting domestic phone calls and electronic communications.