US released a statement demanding Nasr "apologise to all victims of Hezbollah terrorism whose loved ones don't share her sadness over the passing of one of Hezbollah's giants".

The text was swiftly removed from her Twitter feed, but by then it had been heavily circulated, with criticism mounting.

Nasr responded on Tuesday with a blog on the CNN website, calling her initial message "simplistic" and "an error of judgment". Her respect for the ayatollah, who she had interviewed for Lebanese television in 1990, was owing to his stance on women's rights, notably his demands that "honour killings" stop, she explained.

But this was not enough. The next day, Nasr was reportedly called in to see her bosses at CNN's headquarters in Atlanta. The New York Times quoted an internal memo froma senior vice-president, Parisa Khosravi, which said: "We have decided that [Nasr] will be leaving the company."

The memo added: "At this point, we believe that her credibility in her position as senior editor for Middle Eastern affairs has been compromised going forward."

The company has not confirmed the news, saying only that the tweet "did not meet CNN's editorial standards". A spokesman added: "This is a serious matter and will be dealt with accordingly." Nasr's Twitter account has fallen silent.

Fadlallah, 74, was Hezbollah's spiritual leader when it formed after Israel invaded Lebanon in 1982, though he later distanced himself from the group's ties with Iran.

Nasr, who appeared on camera and worked behind the scenes at the TV station, soon realised her mistake, writing on her blog: "Reaction to my