JERUSALEM, Israel -- Israeli officials said a server malfunction disrupted government websites Sunday, not "Anonymous," an Internet group claiming responsibility for hacking government websites.

According to a video posted on YouTube, the cyber-attack was in response to Israel's interception of a flotilla attempting to break the naval blockade of the Gaza Strip.

Not less than 10 government websites, including the Israel Defense Forces Spokesman's Office, the Mossad (Secret Service) and the Shin Bet (Israeli Security Agency), were affected by the malfunction.

"We can say with 100 percent certainty there was no attack by Anonymous or any other element," said Carmela Avner, who helps manage the interface for the websites.

Avner said a "systematic malfunction of the servers" made a number of government websites inaccessible for a few hours, and "all resources" were working on resolving the problem.

"It has nothing to do with an attack, threat, or hacking," said deputy director of Information Technology Ziv Slater. "It's just a systems malfunction. Our best minds are working to fix the problem."

The video, posted Friday, threatened to retaliate against Israel's naval blockade via cyber-attacks.

"We do not tolerate this kind of repeated offensive behavior against unarmed civilians," a computerized voice says on the video, referring to the most recent interception of a two-vessel flotilla on Friday.

"If you continue blocking humanitarian vessels to Gaza…then you will leave us no choice but to strike back again and again until you stop," the voice threatens.