The virus is believed to have first taken hold on Tuesday in Ukraine where it silently infected computers after users downloaded a popular tax accounting package or visited a local news site, national police and international cyber experts said.
More than a day after it first struck, companies around the world were still wrestling with the fallout while cyber security experts scrambled to find a way to stem the spread.
Danish shipping giant A.P. Moller-Maersk (MAERSKb.CO) said it was struggling to process orders and shift cargoes, congesting some of the 76 ports around the world run by its APM Terminals subsidiary.
U.S. delivery firm FedEx Corp (FDX.N) said its TNT Express division had been significantly affected by the virus, which also wormed its way into South America, affecting ports in Argentina operated by China's Cofco.
The malicious code locked machines and demanded victims post a ransom worth $300 in bitcoins or lose their data entirely, similar to the extortion tactic used in the global WannaCry ransomware attack in May.
More than 30 victims paid up but security experts are questioning whether extortion was the goal, given the relatively small sum demanded, or whether the hackers were driven by destructive motives rather than financial gain.
Hackers asked victims to notify them by email when ransoms had been paid but German email provider Posteo quickly shut down the address, a German government cyber security official said.
Ukraine, the epicenter of the cyber strike, has repeatedly accused Russia of orchestrating attacks on its computer systems and critical power infrastructure since its powerful neighbor annexed the Black Sea peninsula of Crimea in 2014.
The Kremlin, which has consistently rejected the accusations, said on Wednesday it had no information about the origin of the global cyber attack, which also struck Russian companies such as oil giant Rosneft (ROSN.MM) and a steelmaker.
"No one can effectively combat cyber threats on their own, and, unfortunately, unfounded blanket accusations will not solve this problem," said Kremlin spokesman Dmitry Peskov.
ESET, a Slovakian company that sells products to shield computers from viruses, said 80 percent of the infections detected among its global customer base were in Ukraine, with Italy second hardest hit with about 10 percent.
