Satire American news website
Screenshots posted by eHacking News indicated a group calling itself the Syrian Electronic Army took control of the feed and posted comments and photos in line with similar intrusions at other news organisations.
"UN retracts report of Syrian chemical weapon use: 'Lab tests confirm it is Jihadi body odour,'" said one tweet, still available in a screenshot on news blogs after being deleted.
Another tweet said: "UN's Ban Ki Moon condemns Syria for being struck by israel: 'It was in the way of Jewish missiles.'"
The Onion did not respond to an AFP request for comment, and some comments on Twitter questioned whether the incident was a hoax by the organisation itself.
"Either @TheOnion has been hacked by the Syrian Electronic Army, or this is its most convincing stunt ever," one tweet said.
Another user tweeted: "The Onion's Twitter feed has been hacked and yet it is still a more reliable news source than CNN."
The Syrian Electronic Army, which appears to be aligned with the government of President Bashar al-Assad, has previously claimed credit for hacking Agence France-Presse, the Associated Press and other news organisations .