The US National Security Agency obtained over 200 foreign phone numbers for surveillance from a US government official, including 35 phone numbers of world leaders, according to a classified memo dated 2006 obtained by The Guardian, provided to the newspaper by former NSA contractor Edward Snowden.  As The Guardian reports, these telephone numbers were given to the NSA by an unnamed US government official outside of the spy agency. And far from being an irregular occurrence, the NSA is said to have actively encouraged other US government officials who are in regular contact with foreign officials — such as members of the US State Department, the Defense Department, even the White House  — to voluntarily hand over the phone numbers of "leading foreign politicians" to the NSA for the purposes of surveillance.

"In one recent case, a US official provided NSA with 200 phone numbers to 35 world leaders," reads the memo. "S2 [Signals Intelligence] Operations Staff immediately supplied this information to the S2 Production Centers." The memo says that many of the numbers would have been available from other sources, but 43 were new. The memo notes that "little reportable intelligence" came from the numbers noted above, which "appear not to be used for sensitive discussions." They had, however, connected the NSA to other numbers that were then tracked as well. "This success leads S2 to wonder if there are NSA liaisons whose supported customers may be willing to share their 'Rolodexes' or phone lists with NSA as potential sources of intelligence," it continues. "S2 welcomes such information!"

The allegations are arguably the most explosive yet to come from the massive trove of leaked documents obtained by Snowden, and come the day after German Chancellor Angela Merkel was reported to have called US President Barack Obama directly over concerns that the NSA was spying on her phone conversations. It's unclear from the leaked memo obtained by Snowden whether Merkel was among the 35 foreign leaders whose numbers had been turned over to the NSA. White House Press Secretary Jay Carney released a statement yesterday saying that the US was not and would not spy on Merkel going forward, but his statements were ambiguous when it came to potential NSA surveillance of the German leader in the past.

The news also comes the same day that an Italian newspaper published allegations that the NSA was spying on millions of that country's residents, and days after the NSA was reported to be conducting similar broad surveillance of phone lines in France, which the agency denied. Today also marks the start of a European Union summit in Brussels wherein leaders are supposed to be debating the future of data protection on the content. The latest leaks seem conveniently timed to influence their decision-making process, especially as Merkel has continued to question the US' behavior.  "We need trust, and now the trust has to be reestablished," she said upon arriving at the summit this morning. "Spying among friends is never acceptable. Now we have to discuss what sort of data protection do we need and what sort transparency is there."

Adi Robertson contributed to this report.