Container shipping company A.P. Moller Maersk on Tuesday said it expects that computer issues triggered by the NotPetya cyberattack will cost the company as much as $300 million in lost revenue.

"In the last week of the [second] quarter we were hit by a cyber-attack, which mainly impacted Maersk Line, APM Terminals and Damco," Maersk CEO Soren Skou said in a statement. "Business volumes were negatively affected for a couple of weeks in July and as a consequence, our Q3 results will be impacted. We expect that the cyber-attack will impact results negatively by USD 200-300m."

Maersk Line was able to take bookings from existing customers two days after the attack, and things gradually got back to normal over the following week, the company said. It said it did not lose third-party data as a result of the attack.

Maersk first announced that it had been hit by NotPetya — a ransomware attack that prevented people from accessing their data unless they paid $300 in bitcoin — in late June. Merck and WPP also said NotPetya had affected operations.

The ransomware took advantage of certain security vulnerabilities in Windows that Microsoft patched after they leaked.

"This cyber-attack was a previously unseen type of malware, and updates and patches applied to both the Windows systems and antivirus were not an effective protection in this case," Maersk said on Tuesday. "In response to this new type of malware, A.P. Moller Maersk has put in place different and further protective measures and is continuing to review its systems to defend against attacks."