JERUSALEM — A widespread hacker attack targeting Israeli websites disrupted government, academic and private sites Sunday.

Officials said strategic infrastructure appeared to have largely repelled the attacks.

Hundreds of websites have been attacked, and more than a dozen government sites have been temporarily disabled since the attack began.

The attack — tagged #OpIsrael by hackers affiliated with the hacker group Anonymous — was announced in advance and described by its organizers as an act of solidarity with Palestinians in retaliation for Israel’s treatment of them and for Israeli settlements and what is perceived as disrespect for international law.

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Several government websites, including those of the ministries of education, defense and environmental protection, were disabled overnight, defaced with anti-Israeli messages and loud music.

Financial and other institutions reportedly blocked access to their servers from abroad the night before, minimizing the risk of being breached from outside Israel.

Hackers did not take down any important or protected sites, according to Yitzhak Ben-Yisrael, head of the country’s National Cyber Bureau. “Anonymous doesn’t have the skills to damage the country’s vital infrastructure,” Ben-Yisrael told Israeli media Sunday.

Despite officials’ claims of only minor disruptions, a Facebook post from the organizers said the attack was a “complete success.”

Preparations for #OpIsrael reportedly began after the November military assault on the Gaza Strip in response to rockets fired into Southern Israel.

Activists warned that “elite cyber-squadrons” would “disrupt and erase Israel from cyberspace” on April 7. Before the attack, hackers posted lists of thousands of sites to be targeted — mostly government and academic domains but including some small private or commercial sites.

Israeli hackers were reportedly fighting back by defacing a site affiliated with Anonymous and replacing pro-Palestinian content with messages of support for Israel and its military.

In Israel, break-ins of websites, hacking of databases and defacement have been on the rise. In addition, Israelis have reported increasing email and Facebook attempts to introduce viruses, malware and spyware.

In one incident, an email message originating from a fake Israeli military sender included an attachment intended to turn computers into carriers of a spamming attack against the Bank of Israel.