Hackers took over Twitter accounts of the New York Post and United Press International, writing bogus messages, including about hostilities breaking out between the United States and China.
One tweet posted under the UPI account on Friday quoted Pope Francis as saying, "World War III has begun."
Another message delivered on the Post account said the USS George Washington, an aircraft carrier, was "engaged in active combat" against Chinese warships in the South China Sea.
The tweets were subsequently deleted. Z
A tweet from the News Corp-owned Post later noted: "Our Twitter account was briefly hacked and we are investigating."
The fake tweets were not just about war. One posted on UPI said "Just in: Bank of America CEO calls for calm: Savings accounts will not be affected by federal reserve decision."
UPI later acknowledged it was hacked, and said "six fake headlines were posted in about 10 minutes".
On Twitter, UPI noted that "World War III has not started, thankfully".
Several media organisations have had their Twitter feeds hacked in the past two years, including Agence France-Presse and the BBC.
Also this week the Twitter feed for the Pentagon's Central Command was taken over by a group supporting the Islamic State jihadists.
A Pentagon official said the tweet about hostilities with China was "not true".
