The European Commission said today it will be conducting a hasty security sweep of its buildings for American bugs after more leaked documents from ex-National Security Agency contractor Edward Snowden described a vast U.S. spying program that targeted the offices of adversaries and allies alike.
"In light of the allegations... [E.U.] President [Jose] Barroso has instructed the competent commission services to proceed to a comprehensive ad hoc security sweep and check," E.U. spokesperson Pia Ahrenkilde told reporters today. "This is disturbing news. If proven true, they demand full clarification."
The German newspaper Der Spiegel first reported on America's alleged efforts to spy on the European Union Saturday, saying their story was based on secret documents obtained and provided to them by Snowden. Snowden, who claims to have been the source for a slew of stories in several major newspapers that revealed what he called the U.S. government's "horrifying" domestic and foreign surveillance programs, is believed to be in hiding in a Moscow airport, having fled there from Hong Kong last month.
READ: Edward Snowden Blasts Obama 'Deception,' WikiLeaks Says
According to the Der Spiegel report, a 2010 document suggests that in addition to installing listening devices in European Union buildings in downtown Washington, D.C., the Union's computer network was also compromised by the U.S. Similar efforts were made against the Union's representatives to the United Nations in New York, and the documents say the U.S. used electronic eavesdropping in target offices in Brussels, host of the European Commission, years ago.
A day after Der Spiegel's report, The Guardian provided additional details on the alleged spying effort, revealing that in one document 38 embassies and missions were described as "targets," including France, Mexico, India, South Korea and Turkey.
The Guardian said one of the documents from 2007 described a bugging method codenamed Dropmire in which a listening device is implanted in encrypted fax machines -- the machines used to send cables to the foreign ministries of European capitals. The codename for the operation to spy on delegates of the E.U.'s United Nations team was "Perdido," or "lost" in Spanish, the paper said.
Along with E.U. spokesperson Ahrenkilde, several top foreign leaders have demanded an explanation from the U.S.
"The monitoring of friends -- this is unacceptable. It can't be tolerated," German Chancellor Angela Merkel's spokesperson Steffen Seibert said on behalf of the German leader, according to Der Spiegel. "We are no longer in the Cold War."
Russian President Vladimir Putin told reporters today his government has evidence of U.S. spying at its embassy but declined to elaborate.
U.S. Secretary of State John Kerry said today that his attention has been on the Middle East in the past few days, and he yet to see the reports.
"I want to see the allegations, number one, and then number two, I need to find out what the truth, what the situation is," Kerry said, promising to give foreign leaders an answer. "I will say that every country in the world that is engaged in international affairs of national security undertakes lots of activities to protect its national security, and all kinds of information contributes to that. All I know is that that is not unusual for lots of nations."
Also over the weekend, The Washington Post published more slides to help explain the NSA program, called PRISM, designed to allow them access to vast amounts of online information by gaining access to major online companies like Google and Facebook.
The alleged source behind each of these headline-grabbing reports, 30-year-old Edward Snowden, was last believed to be hiding out in the transit area of a Moscow airport and in the eye of a complex diplomatic storm.
The U.S. has revoked his passport and charged him with espionage. Hong Kong, where Snowden revealed himself as the leaker last month, has already been blasted by the U.S. for allowing him to leave there.
Putin last week denied strongly-worded U.S. requests to arrest Snowden and turn him over, saying Snowden was a "free person" and technically hadn't entered Russia. Still, Putin indicated he wanted Snowden out of his hands quickly, saying it would better for him and for Russia if he would go.
At the time, it was reported that Snowden had been given refugee travel documents by the Ecuadorian Embassy in London, meaning he wouldn't have to rely on his U.S. passport, but over the weekend Ecuadorian President Rafael Correa said the issuing of the document was a "serious error" committed without consultation with his government in Quito.
Snowden was originally believed to have planned to fly from Moscow to Cuba and from there to Ecuador, which was one of some 15 different countries to which he applied for asylum. But Snowden has missed several flights to Havana already and has not been seen by reporters on the ground in Moscow.
Today Putin said that Snowden would be allowed to stay in Russia, but only as long as he stops harming U.S. interests.
"If he wants to stay here, there is one condition: He has to stop his work aimed at damaging our U.S. partners, no matter how strange this sounds coming from me," Putin said.
A Russian official confirmed to ABC News that Snowden has applied for political asylum there, one of a reported 15 countries Snowden apparently will help him out of his conundrum. The New York Times reported the application had not yet been received by Russia's foreign ministry.
The U.S. State Department today dismissed the idea that Snowden was trapped in the Russian airport and said he is free to come back to the U.S. to face a "free and fair trial."
"We reject the notion that this is some sort of political prosecution, indeed, it's not," State Department spokesperson Patrick Ventrell told reporters. "He's still a U.S. citizen. He still enjoys the rights of his U.S. citizenship, which include the right to a free and fair trial for the crimes he's been accused of [committing]."
Putin reiterated that Russia has no plans to extradite Snowden and said again that his security service is not working with or cooperating with Snowden.
U.S. officials told ABC News last month that they feared first Chinese and then Russian intelligence agents would gain access to Snowden's trove of secrets.
The head of the Russian Security Council told a Russian television station today that President Obama and President Putin have decided that their respective internal security services, the FBI and FSB, would be the ones to sort out what's to be done about Snowden.
ABC News' James Gordon Meek and Dana Hughes contributed to this report.