Spain's prosecutor's office says it has opened a preliminary inquiry into allegations that Spain was a target for surveillance by the U.S. National Security Agency.
The office said Tuesday the inquiry aims to establish whether a crime was committed and if Spain should consider opening a formal investigation. The inquiry may take weeks.
On Monday, El Mundo newspaper published a document it said showed the NSA tracked more than 60 million phone calls in Spain in one month alone, the latest revelation about alleged massive U.S. spying on allies.
Spain insists it is unaware of any U.S. spying but has said it is confident Washington will provide a full explanation. It has warned that if the allegations are confirmed it could break the climate of mutual trust.