The shadowy National Security Agency said late Friday that it was a glitch that brought down its public website for a few hours, not hackers as some claimed online.

"NSA.gov was not accessible for several hours tonight because of an internal error that occurred during a scheduled update," the spy agency said in an emailed statement. "The issue will be resolved this evening. Claims that the outage was caused by a distributed denial of service [DDoS] attack are not true."

Earlier this evening online server trackers noted the NSA's website had been down for at least six hours, and the site continues to be inaccessible for some users. Earlier an NSA spokesperson told ABC News the agency's internal, sensitive network was "not at all" compromised. No classified information is in danger, the spokesperson said.

At least one hacktivist group online claimed that they were responsible for bringing down the NSA site with a DDoS attack. DDoS attacks are designed to flood a target website with traffic until the servers are overloaded and the site collapses. The cyber tactic is a relatively unsophisticated one and the attacks are not meant to penetrate the internal network of the target system.

The formerly super secretive NSA, once nicknamed No Such Agency, has found itself in very public light, and amid vicious criticism, in past months following a stream of revelations about is vast foreign and domestic surveillance programs - collectively the product of secret NSA files stolen from the agency and leaked by disenchanted former NSA contractor Edward Snowden.

Such growing controversy surrounding the agency prompted early speculation that tonight's incident was the result of a targeted cyber operation.

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