Saudi banking officials have denied reports in Israeli media that hackers have brought down the Saudi Stock Exchange (Tadawul) and the Abu Dhabi Securities Exchange (ADX).
A top official in the Saudi banking authority said he had received no reports of customer data breach. Earlier reports by Israeli news website Haaretz suggested that the Israeli hackers, who go under the name of the IDF Team, took down Tadawul's website and caused delays on the ADX exchange site.
The attack was in retaliation for the hacking of the Tel Aviv Stock Exchange website, El Al Airlines and three banks on Monday. The hackers warned that if the attacks continued they would "move to the next stage and paralyse websites for a period of two weeks to a month".
The Saudi hacker who has been at the forefront of the recent cyber-war against Israel pledged to continue to strike until the government "apologised for their genocide in Palestine and Gaza".
He said he had joined the forces with a group of pro-Palestinian hackers called "Nightmare" who claimed responsibility for attacking and shutting down the Tel Aviv Stock Exchange.
A spokeswoman for the exchange confirmed that the site had been attacked but said trading systems had not been affected.
"There is someone that has been attacking the Tel Aviv Stock Exchange website since this morning," Idit Yaaron told AFP. He described what appeared to be a distributed denial of service attack (DDos).
Hacker 0xOmar warned he was going to attack the websites, Israeli newspapers reported.
0xOmar's first attack happened on 3 January when he claimed to have posted details of 400,000 Israeli-owned cards online.
Israel's main credit card companies admitted that 20,000 cards had been hacked.