Israeli hackers on Tuesday claimed to have taken down the Saudi Arabian and UAE stock exchange websites. The group of hackers, who call themselves IDF Team- an acronym for Israeli Defence Forces, was able to temporarily paralyse the two websites.

The IDF Team said that the hits came in retaliation for an attack on Monday by a group of Saudi-based hackers, named Nightmare, who shut down the sites for Tel Aviv stock exchange and Israeli airline El Al’s.

The  hackers warned in a statement: “Pathetic hackers from Saudi Arabia decided to launch an attack against Israeli sites (…) if these continue, we will move to the next level, which will disable these sites longer term (…) to weeks or even months. You have been warned.”

The actions taken by hackers involved appear to be the beginning of a cyber war, with both sides willing to release hacked data to the public.

Israel’s foreign minister, Danny Ayalon, said that hacking attacks are “comparable to terrorism,” and will require a forceful response.