Hackers from Anonymous claim to have attacked NATO and obtained a gigabyte of data. (AP)

This post has been updated since it was originally published.

Hacker collective Anonymous posted on its Web site that it has taken a gigabyte of data from NATO.

On a Twitter feed believed to be run by the group, a Thursday morning message said that the hackers had obtained a lot of material that would be “irresponsible” to publish.

So far, the group has posted two documents on its Twitter feed. One of the documents is headed with the words “NATO Restricted.”

Another document posted by the group, titled “Outsourcing CIS in Kosovo,” appears to be from 2008. Hackers said that it was relatively easy to get the information.

We are sitting on about one Gigabyte of data from NATO now, most of which we cannot publish as it would be irresponsible. But Oh NATO....Thu Jul 21 11:57:54 via Power TwitterAnonymousIRC

The FBI arrested 14 people believed to be active members of the hacking group Tuesday, along with two men linked to information that was posted by LulzSec, a similar hacking group.

Anonymous promised to release more information from NATO over the next few days.

In response to the attacks, a NATO spokesman told Post reporter Ellen Nakashima: “NATO is aware that a hackers group has released what it claims to be NATO classified documents on the internet. NATO security experts are investigating these claims. We strongly condemn any leak of classified documents, which can potentially endanger the security of NATO Allies, armed forces and citizens.”

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