The New York Post newspaper said Friday that some of its Twitter accounts had been hacked, with posts going out that reported false economic and military news.
Suspicious tweets also appeared on a Twitter feed belonging to United Press International. One tweet on UPI's feed said the pope had announced the start of "World War III."
The Post said the hack was being investigated. There was no immediate comment from UPI.
The apparent cyberattacks came just days after hackers attacked the Twitter and YouTube accounts of U.S. Central Command, which oversees U.S.-led airstrikes on Islamic State militants in Iraq and Syria. The hackers said they were loyal to the Islamic State group.
Cybersecurity has made headlines since the November 24 hacking of Sony Pictures Entertainment. That attack, which U.S. investigators traced to North Korea, led to the leaks of unreleased films and embarrassing internal emails.
President Barack Obama said the hack destroyed data and computer hardware that will be "very costly" for Sony to clean up.
Obama is now calling for new cybersecurity legislation to promote greater information sharing between the government and private companies.