Cities across Israel were hit by a huge power failure on Thursday afternoon in a suspected cyber attack.
The Anonymous Sudan hacker group said it was responsible for the incident, boasting on its Telegram channel that "the electric attack was just for fun. We'll show you more".
In a later post, the group threatened more attacks: "Israel, we are still playing with you ... soon you will be without the internet. We are working to down the internet in Israel like electricity."
Israel's Electric Company told The National that a fault in a production unit caused the failure.
In a statement, the company said: "Due to a glitch in one of the Haifa power plants, power outages are being felt in a number of areas around the country ... regular power supply was renewed to a number of areas and will be fully renewed in the next few minutes."
The outage caused major traffic jams in Tel Aviv, as right-wing protesters prepared to attend a rally to show support for the country's government.
During recent months Anonymous Sudan has been behind several cyber attacks in Israel, including during Wednesday's celebrations of the 75th anniversary of the establishment of Israel, in which two news sites and Israel's Defence Ministry and Shin Bet security service were claimed to be attacked.
The Facebook account of Israeli Prime Minister Benjamin Netanyahu was also targeted. The page was briefly full of Arabic-language Quranic verses.
Earlier in April, a series of hacks hit important websites, including those of Ben-Gurion Airport and a number of universities.
Israeli authorities later blamed some of them on Iran, including one on Haifa's prestigious Technion Institute, in which hackers demanded millions of shekels as a ransom.