French President Francois Hollande told the United States on Monday to immediately cease spying on European institutions, after reports of covert US surveillance of EU diplomatic missions.
"We cannot accept this kind of behaviour between partners and allies," Hollande told journalists during a visit to the western city of Lorient. "We ask that this immediately stop."
Hollande said "enough elements have already been gathered for us to ask for explanations" from Washington about the spying allegations.
German news weekly Der Spiegel reported that the US National Security Agency (NSA) carried out covert surveillance on EU diplomatic missions, basing its report on confidential documents, some of which it had been able to consult via fugitive US leaker Edward Snowden.
The European Union, Paris and Berlin have angrily demanded answers over the allegations.