Global shipping line CMA CGM says it suspects there has been a data breach following a cyber attack affecting its servers, the company said on Wednesday.

"We suspect a data breach and are doing everything possible to assess its potential volume and nature," it said in a statement.

The company gave no further details about the suspected data breach.

CMA CGM, the world's fourth-largest container shipping company with headquarters in France, first reported the incident on Monday, saying it had shut down access to its online services after malware targeted its peripheral servers.

The group's e-business website remained unavailable, with customers directed to alternative channels.

However, the company said on Wednesday: "Today, the back-offices (Shared Services Centers) are gradually being reconnected to the network thus improving the bookings’ and documentation’s processing times."

The company's technical teams, alongside independent experts, are continuing the investigation.

Market leader Maersk suffered a serious cyber attack three years ago that also disrupted its port terminal operations. And in April, MSC Mediterranean Shipping Company reported a cyber attack that caused a network outage at its headquarters in Geneva, Switzerland. 

CMA CGM said on Tuesday that its maritime and port operations were functioning normally, adding that the malware attack had not compromised any of its communications.

The attack did not concern the systems of its subsidiary CEVA Logistics, it said following the cyber attack.

Lloyd’s List reported that the cyber incident is a ransomware attack by the “Ragnar Locker gang”.