Pro-Palestine cyberattackers have targeted Israeli government websites, in an assault dubbed Operation Israel.
The government says the attackers caused no serious disruption. But after 2pm this afternoon, the website for the Israeli parliament, the Knesset, was down. It was not clear whether it had been hacked.
Yesterday the loosely-knit hacking group Anonymous posted an online video addressed to the Israeli government. In it, they said: "You have shown that you do not respect international law.
"This is why that on April 7, elite cyber-squadrons from around the world have decided to unite in solidarity with the Palestinian people against Israel as one entity to disrupt and erase Israel from cyberspace." That last comment echoes a statement by Iranian president Mahmoud Ahmadinejad that the Jewish state should be "wiped off the map."
Early this afternoon during the attack - which is ongoing - a Twitter account called @Op_Israel tweeted: " THIS IS NOT JUST HACKING, THIS IS A WAR FOR OUR FREEDOM."
Yitzhak Ben Yisrael, of the Israeli government's National Cyber Bureau, said hackers had mostly failed to shut down key sites.
He said: "So far it is as was expected, there is hardly any real damage.
"Anonymous doesn't have the skills to damage the country's vital infrastructure. And if that was its intention, then it wouldn't have announced the attack of time. It wants to create noise in the media about issues that are close to its heart."
Israel's Bureau of Statistics was down early on today but it was unclear if it had been hacked.
Media reports also said the sites of the Defence and Education Ministry as well as banks had come under attack the night before but were mostly repelled.
Haaretz newspaper said almost 19,000 Israeli Facebook accounts had been attacked by hackers affiliated with Anonymous.
Last November, hackers broke into Israeli websites during fighting in Gaza but failed to cause serious disruption, according to AP news agency.