The Saudi Arabia and Abu Dhabi stock exchanges have been targeted by hackers.

Both exchanges reportedly their websites either taken down or significantly slowed, in response to an online attack on Monday on Israel's Tel Aviv Stock Exchange and on Israeli national airline El Al. Israeli ministers have already branded the web attacks on the country's businesses as similar to "terrorism", and blamed Saudi hackers.

The news marks a growing form of political protest online, in which large businesses and government institutions are targeted. In another hack last week, the credit card details of thousands of Israeli nationals were posted on the web.

Yesterday's hack of the Saudi Arabian Tadawul and the Abu Dhabi ADX exchange sites was carried out by IDF Team, a hacking group based in Israel.

Users of the Tadawul website said the site was taken offline, though the exchange insisted that it has continued to function. ADX's page loading was significantly slowed.

"If the lame attacks from Saudi Arabia will continue, we will move to the next level which will disable these sites longer term [and] may come to weeks or even months," wrote IDF Team in a forum. "You have been warned."