Trading in FedEx shares was halted for nearly an hour Wednesday ahead of the announcement, although operations of the parent company and other units were not impacted.
FedEx said TNT's operations were "significantly affected" by the information system virus, which was causing delays at TNT Express' domestic, regional and inter-continental services.
"While TNT Express operations and communications systems have been disrupted, no data breach is known to have occurred," FedEx said in a statement.
"Remediation steps and contingency plans are being implemented as quickly as possible."
The hacking did not affect FedEx operations, and the company said it could not yet estimate the financial impact of the disruption, but said "it could be material."
Shares of FedEx rose 1.1 percent at $216.61 at midday.
Thousands of computer users across the globe scrambled to reboot on Wednesday after a fresh wave of ransomware cyberattacks spread from Ukraine and Russia worldwide on Tuesday.
Besides TNT, others hit included Russian oil giant Rosneft, global shipping firm Maersk, British advertising giant WPP, and US drug giant Merck.
Eyewitness? Submit your stories now via social or:
Email: news@pulselive.co.ke
