A number of Israeli websites were hacked Tuesday to display pro-Palestinian messages in what experts said was the start of the annual cyberattack by the hacker collective known as “Anonymous.”

Homepages for the municipality websites for Kfar Saba, Eilat, Herzliya and Acre were changed to display the message: “Jerusalem is the capital of Palestine” alongside an image of the deadly clashes between Palestinian protesters and Israeli forces along the Gaza border over the weekend.

The pages, that were set to music, also displayed the Arabic message “We will not forget our martyrs.”

Get The Times of Israel's Daily Edition by email and never miss our top stories Free Sign Up

Websites for Israel’s national opera, a hospital in Hadera and the local council for the city of Gan Yavne were also defaced.

Cyber defense expert Einat Meron told Hadashot news the hacked websites bore the hallmarks of Anonymous’s annual OpIsrael cyber campaign, targeting websites and social media accounts of the Israeli government and other major organizations in solidarity with the Palestinians.

“This is part of a wider attack that exploits technology, but it really is about influencing public opinion,” Meron said, urging companies and government agencies to take necessary security precautions.

A senior security researcher for Russia’s Kaspersky’s Lab also told the TV station that Anonymous was likely behind Tuesday’s hacks.

“In recent days we have seen extensive planning on social media and on forums associated with extremists regarding Anonymous’s annual attack on Israeli targets,” Ido Naor said. “It seems that Islamic groups have already begun attacks in the last few hours.”

Anonymous hackers have waged the opIsrael campaign since 2013, but have failed to case any major disruptions in internet services or to bring down any major government websites.