An upcoming story in the Spanish newspaper El Mundo reports that the U.S. National Security Agency swept up data on 60 million phone calls in Spain over the course of one month in 2012.

This latest revelation comes from documents uncovered by NSA whistleblower Edward Snowden.

Earlier on Sunday, Greenwald teased the story in a tweet. He later revealed that the country in question is Spain, and he tweeted a screenshot of the story on El Mundo's front page.

This newest surveillance news is likely to further inflame international tensions surrounding the intelligence reach of the U.S. government. It comes on the heels of another story co-written by Greenwald, this one from France's Le Monde newspaper. The Le Monde report indicated that the NSA collected 70 million French telephone records over a 30-day period.

Also this week, a separate story revealed that the U.S. might have bugged the phone of German Chancellor Angela Merkel for over a decade.

The NSA has denied reports that its Director Keith Alexander had briefed Obama on the matter as far back as 2010.