One tweet posted under the UPI account 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.
A tweet from the News Corp-owned Post later noted that "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 in a dispatch that "six fake headlines were posted in about 10 minutes."
On Twitter, UPI noted that "World War III has not started, thankfully."
Several media organizations have had their Twitter feeds hacked over 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."
Get your daily dose of tech news, reviews, and insights, in under 80 characters on Gadgets 360 Turbo. Connect with fellow tech lovers on our Forum. Follow us on X, Facebook, WhatsApp, Threads and Google News for instant updates. Catch all the action on our YouTube channel.
Samsung Galaxy Watch 9 (44mm, LTE)
Starts from ₹44,999
Samsung Galaxy Watch 9 (40mm, LTE)
Starts from ₹37,999
Samsung Galaxy Watch 9 (40mm)
Starts from ₹37,999
Haier M70 Mini LED 65-inch
Starts from ₹74,990
CMF Buds Neo True Wireless Stereo (TWS) Earphones
Starts from ₹2,199
Xiaomi TV FX Mini LED 65
Starts from ₹64,999
IFA 2026: Lenovo Unveiled New IdeaPad, Yoga and ThinkBook Laptops
IFA 2026: Nvidia RTX Spark PCs, Local AI Tools Announced With October Launch Planned
Luna Band Now Available Globally: Check Price in India, Specifications and Features