Earlier this week a hacking collective called Nightmare hit the Web sites of the Tel Aviv Stock Exchange, banks and El Al, the Israeli national airline.

In a message posted on Pastebin, a group calling itself IDF-Team yesterday warned that "because of the lame hackers from Saudi Arabia" it would attack the Saudi Stock Exchange (Tadawul) and the Abu Dhabi Securities Exchange (ADX).

According to local press reports, the Tadawul site was duly paralysed while the ADX portal suffered significant delays.

However, in a notice on its site today, the Tadawul claims: "Media reports about any hacking of Tadawul website and/or any associated degradation of website performance are incorrect. The exchange website remains accessible and fully operational to users."

The tit-for-tat attacks on bourse sites are the latest salvos in a conflict that began when OxOmar, a member of Saudi hacking collective Group-XP, posted the personal information, including some credit card details, of around 400,000 Israelis.

Last week an Israeli hacker hit back by publishing details of around 200 Saudi credit cards, while the country's deputy foreign minister compared the initial incident to terrorism and threatening retaliation against the perpetrators.

Since then Sami Abu Zuhri, a spokesman for Hamas - the group that controls Gaza and is considered a terrorist organisation by Israel and the US - has stoked the fires further by claiming: "Penetrating Israeli websites means opening a new field of resistance and the beginning of an electronic war against Israeli occupation."

IDF-Team has now warned that is prepared to take further action, insisting: "If the lame attacks from Saudi Arabia will continue, we will move to the next level which will disable these sites longer term may come to weeks or even months."