Hackers claiming to be from the Gaza Strip defaced the website of the Israel Fire and Rescue services, posting a message saying "Death to Israel," a spokesman told AFP on Friday.
Fire service spokesman Yoram Levy said that attackers who identified themselves as the "Gaza Hackers Team" struck its website late on Thursday and posted a picture of Israel's Deputy Foreign Minister Danny Ayalon with footprints over his face.
"There was some writing in Arabic and a picture of Danny Ayalon," Levy said, adding that by Friday morning the site was largely back to normal.
Last week, Ayalon said Israel would respond to cyber-attacks in the same way it responds to violent "terrorist" acts after hackers claiming to be from Saudi Arabia published details of tens of thousands of Israeli-owned credit cards online.
Two days later, Ayalon's website was briefly taken down after coming under attack, allegedly by hackers from Gaza, in an incident he blamed on "Muslim extremists."
The latest incident follows a string of tit-for-tat hacking attacks which began on January 3 when a Saudi hacker called 0xOmar said he had posted details of 400,000 Israeli-owned cards online.
Three days later, he said he had published another 11,000 card details but it turned out to be malware that infected anyone who downloaded the information.
Signup to our newsletter and follow us on Facebook and Twitter!
Israel's main credit card companies said about 20,000 valid cards had been affected.
Earlier this week, an Israeli hacker "0xOmer" launched a counter-attack and posted details of 217 Saudi cards online, prompting another attack by the Saudi hacker who urged Arab and Muslim hackers to wage cyber warfare on the Jewish state.
In his latest message posted on Pastebin.com early on Friday, 0xOmar hailed the Gaza hackers behind the attack on Ayalon's website and threatened to expand the attacks on Israel.
"From here, I send my thanks to Gaza hackers who have successfully hacked stupid Danny Ayalon website," the Saudi hacker wrote.
"This is the beginning of cyber war against Israel, you are not safe any more. We'll hack Israeli servers for different purposes like leaking Israeli data, sensitive and hidden information extraction and defacing web sites."
Meanwhile, a report in the English-language Jerusalem Post said the military was recruiting elite teams of hackers to spearhead the fight against cyber attacks.
Last month, the army recruited nearly 300 young computer experts to serve in Military Intelligence as well as in the C4I Directorate -- the two units responsible for the army's cyber warfare efforts.
"We are not where we would like to be when it comes to the cyber world and we are working to improve our capabilities," a senior officer told the paper.