Health insurer Medibank Private has been hit by a cyber attack. 

Medibank Private says “unusual activity” was detected on its network on Wednesday, but claimed sensitive data, including customer information, appears not to have been accessed. 

Still, a number of customer-facing systems were taken down, causing disruptions for some customers.

Chief executive David Koczkar says Medibank is aware of its responsibility to protect sensitive data it holds about people's health. 

“I apologise and acknowledge that in the current environment this news may make people concerned,” he said. 

“Our highest priority is resolving this matter as transparently and quickly as possible.”

Medibank says investigations into the cyber attack are ongoing, and has requested a trading halt on the ASX while it investigates.