(Adds details, Rosneft, Ukraine)
COPENHAGEN, June 27 (Reuters) - Shipping company A.P. Moller-Maersk reported a computer systems outage on Tuesday which it said could be a global issue.
"We can confirm that Maersk IT systems are down across multiple sites and business units. We are currently assessing the situation," Maersk said on Twitter.
A Maersk spokeswoman said the cause of the breakdown was not yet known, but that it could extend across the company's global operations.
Russia's top oil producer Rosneft said on Tuesday its servers had been hit been a large-scale cyber attack, but its oil production was unaffected.
Ukraine's central bank also said a number of Ukrainian commercial banks and state and private companies had been hit by cyber attacks via an "unknown virus".
(Reporting by Jacob Gronholt-Pedersen; editing by Jason Neely)