Pro-Palestinian cyber attackers were not behind the collapse of the websites of several Israeli security agencies yesterday, a government spokesman said.

On Friday, the international hacker group Anonymous posted a video on YouTube stating that Israel's decision to intercept the boats of activists attempting to reach Gaza would "not go unnoticed by us or the people of the world".

They added: "You will leave us no choice but to strike back. Again and again, until you stop. Expect us."

On Sunday, the websites of Mossad, Shin Vent and the IDF spokesman could not be accessed. The government said the problem was "being dealt with by experts" and denied that it was a cyber attack.

"It was only a technical malfunction," said Ofir Gendelman from the prime minister's office.

Anyonymous have not claimed responsiblity for what happened. The websites are all working today.