Spanish newspaper El Mundo said the National Security Agency (NSA) had recently tracked over 60 million calls in Spain in the space of a month, citing a document which it said formed part of papers obtained from ex-NSA contractor Edward Snowden.
Speaking at a joint news conference with his Polish counterpart in Warsaw, Spanish Foreign Minister Jose Manuel Garcia-Margallo said: "As in previous occasions, we've asked the US ambassador to give the government all the necessary information on an issue which, if it was to be confirmed, could break the climate of trust that has traditionally been the one between our two countries.
"I had been in touch with (the US ambassador) before this morning's meeting. So far, we have no official indication our country has been spied on."
Madrid has also asked the US to provide more data from the NSA, the foreign ministry said in a statement issued after a meeting between Spain's Secretary of State for the European Union, Inigo Mendez de Vigo, and US Ambassador to Spain James Costos.
US President Barack Obama has ordered a review of US surveillance programmes after Mr Snowden leaked documents that raised alarm in the US and abroad.
Ambassador Mr Costos said: "We will continue to confer with our allies, such as Spain, through our regular diplomatic channels to address the concerns they have raised."
Spain has so far resisted calls from Germany for the European Union's 28-member states to reach a "no-spy deal", after reports the NSA monitored the phone of German chancellor Angela Merkel.
El Mundo reproduced a graphic in yesterday's edition which it said was an NSA document showing the agency had spied on 60.5 million phone calls in Spain between December 10, 2012 and January 8 this year.
The newspaper said it had reached a deal with Glenn Greenwald, the Brazil-based Guardian journalist who has worked with other media on information provided to him by Mr Snowden, to get access to documents affecting Spain.
El Mundo said the telephone monitoring did not appear to track the content of calls but their duration and where they took place. It said the eavesdropping system used by the NSA could also monitor emails and phone texts.
Another Spanish paper, El Pais, said documents provided by Mr Snowden showed the NSA had tracked phone calls, text messages and emails of millions of Spaniards and spied on members of the government and other politicians.
The NSA is reported to have collected the sender and recipient addresses of emails, along with their IP addresses, the message file size, and sometimes the top or subject line of the message.
Mr Snowden is currently living in Russia, out of reach of US attempts to arrest him.
Nine European MEPs are to visit Washington to get more information on the US mass surveillance.
The representatives from the European Parliament's Committee on Civil Liberties, Justice and Home Affairs are expected to speak to members of the US Congress and security officials to gather information about the recent allegations of US spying on European leaders and citizens.
Meanwhile, a Japanese news agency said the NSA had asked the Japanese government in 2011 to help it monitor fibre-optic cables carrying personal data through Japan, to the Asia-Pacific region.
The reports, carried by Kyodo, said this was intended to allow the US to spy on China but that Japanese officials refused.