Credit: CC0 Public Domain

Denmark's biggest news agency that delivers text and photos to Danish media was knocked offline following a hacking attack Tuesday.

"Ritzau has been the target of a hacker attack early this morning. It appears to be a professional attack," the 's CEO Lars Vesterloekke said. "We have now chosen to shut down all our because we were unsure how much damage the attack could cause."

Email and telephones were down and news was instead sent out via an emergency email system. It was unclear who was behind the attack and when the agency would be back online.

Since 1866, Copenhagen-based Ritzau has distributed information and produced news for Danish media, organizations and companies.