Hackers posted a bogus announcement of a rocket strike against Israel's Dimona reactor and a possible nuclear leak on a Twitter account used by the Israeli military, which said on Friday it was combating such cyber attacks.
The English-language account, @IDFSpokesperson, has 252,000 followers and usually scrolls out rapid updates on Israel's various fighting fronts. It was inactive on Friday, however, as a military spokeswoman said "several incorrect tweets" were being investigated by Israeli authorities.
She did not elaborate, but the Walla news site published a snapshot of a tweet that had appeared on the account on Thursday night before being removed. It read: "#WARNING: Possible nuclear leak in the region after 2 rockets hit Dimona nuclear facility."
That referred to a reactor in Israel's southern desert, where it is widely believed to have developed nuclear weapons.
Israeli websites are frequently the target of pro-Palestinian and Syrian hackers and Prime Minister Benjamin Netanyahu has encouraged investment in national cybersecurity.
The most recent authorised tweet on @IDFSpokesman promised the military would "combat terror on all fronts including the cyber dimension".