Anti-Israeli hackers attacked official websites in the Jewish state's mainly Muslim ally Azerbaijan on Monday, the same day as several Israeli sites were also threatened.
Hackers broke into the sites of ex-Soviet Azerbaijan's interior and communications ministries, its governing party and constitutional court, leaving anti-Israeli messages.
They substitued the interior ministry's homepage with an image of the devil looming over a photograph of Azerbaijani President Ilham Aliyev and his Israeli counterpart Shimon Peres shaking hands.
"You are servants of the Jews," said a message on the hacked governing party's site said, threatening Aliyev with the fate of the deposed leaders of Tunisia, Egypt and Libya.
Officials in ex-Soviet Azerbaijan called the attack an assault on the country's leader and launched an investigation.
"These are forces that are scared of Azerbaijan," leading governing party lawmaker Mubariz Gurbanli told AFP.
"Specialists are now working to identify the places and people who did this."
Energy-rich Azerbaijan has a friendly relationship with Israel based on the export of oil and the import of weapons and military technology.
The attack came on the same day as the websites of Israeli national airline El Al and the Tel Aviv Stock Exchange went offline just hours after they were reportedly threatened by a Saudi hacker.
The Tel Aviv Stock Exchange website made a swift recovery and was back online by Monday morning, but the El Al website remained unavailable into the morning.
The Tel Aviv Stock Exchange website made a swift recovery and was back online by Monday morning, but the El Al website remained unavailable into the morning.
The prominent hacker 0xOmar, who has been at the forefront of an Internet assault on Israel, and who released tens of thousands of Israeli credit card numbers last month, sent an email to The Jerusalem Post before the attack.
He said he had been joined by a hacking team called "Nightmare." The new group "promised to take down" the two websites by morning, he added.
El Al released a statement saying it was aware that "a cyber war has been waged against the State of Israel for two weeks. El Al is closely monitoring the activities of the Saudi hacker [0xOmar]." El Al said steps being taken to fortify its official website "could cause disruptions to the website's activities." Both websites supply key information to members of the public, and their attack represents an escalation in the web war being waged against Israel.