JERUSALEM // Pro-Palestinian hackers apologised on Twitter yesterday for disrupting the website of Israel's Haaretz newspaper.

Haaretz announced on Wednesday that its Hebrew-language website had been temporarily disabled by hackers, identifying themselves on Twitter as @AnonPS, or Anonymous Palestine.

The group claimed responsibility shortly after the attack, tweeting: "haaretz.co.il Tango Down :)". But yesterday morning an apology appeared on the same Twitter account "@haaretzprint we are sorry, we didn't know that haaretz is a good newspaper, we sorry about this, and be sure no one will attack u again".

The attack on Haaretz surprised observers. The newspaper is known for documenting the vagaries of Israel's occupation of Palestinian territory.

"It is a bit ironic, you have to admit," Gideon Levy, a Haaretz columnist known for his criticism of the occupation, said by telephone yesterday.

He said the attack knocked out the newspaper's computer systems for several hours.

That irony did not escape other commentators, either, such as Jeffery Goldberg, a former Israeli soldier and writer at The Atlantic, a US magazine.

In a Wednesday Twitter post, he noted: "Pro-Palestinian hackers attack Haaretz website, operating under the mistaken belief that Haaretz is their enemy."

The same day hackers also attacked the websites of other Israeli institutions in the latest round of cyber attacks between the sides of the Israel-Palestinian divide.

The hacking escalated this month with each claiming responsibility for lifting the details of thousands of credit card users and mounting attacks on websites linked to Israel, Saudi Arabia and the UAE.

Anonymous Palestine also claimed an attack on Wednesday against Israel HaYom, Israel's largest-circulated daily, and vowed that it could go after all "government sites, all famous sites, even google.co.il".

The websites of two hospitals in Israel were also brought down on Wednesday, as well as the Israel Festival's site.

On the arts festival's website, hackers posted an icon of the Palestinian flag and "Death to Israel and U.S.A".

Officials suspect the incidents are part of a series of coordinated cyber attacks that, beginning this month, paralysed Israel's El-Al International Airlines and the Tel Aviv Stock Exchange.

Those were followed by hacking attempts by suspected pro-Israel groups on the UAE Central Bank and the Arab Bank Palestine.

Sabri Saidam, a telecommunications adviser to the Palestinian Authority (PA) president, Mahmoud Abbas, expressed concern that the escalating attacks could form a dangerous, new front in the Israel-Palestinian conflict.

"I think 2012 will be the year of electronic hacking and electronic confrontation that puts to an end the legacy of traditional, strategic weapons," he said.

"No matter what measures are taken, they need to be updated regularly. Whatever you install now, ten seconds later it's out of date."

The PA has formed a special committee to look into bolstering Palestinian institutions from such attacks, which he said were escalating and targeting just about "any institution".

He said some of the hackers targeting PA-related institutions seemed to be originating in Israel, which he attributed to "amateur" groups.

Last year, computer hackers launched a sustained attack on telephone and internet networks in the West Bank and Gaza Strip.