New Zealand's central bank said Sunday it was responding with urgency to a "malicious" breach of one of its data systems, a third-party file sharing service that stored "sensitive information".

Reserve Bank of New Zealand governor Adrian Orr said the breach had been contained and the system was taken offline but it would take time to determine what information had been accessed.

"We are working closely with domestic and international cyber security experts and other relevant authorities as part of our investigation and response to this malicious attack," Orr said.

"The nature and extent of information that has been potentially accessed is still being determined, but it may include some commercially and personally sensitive information," he added.

"It will take time to understand the full implications of this breach, and we are working with system users whose information may have been accessed."

In its latest report, the government agency CERT (Computer Emergency Response Team) said cyber attacks had increased 33 percent year-on-year in New Zealand. 

The country's stock exchange was targeted by sustained DDoS (distributed denial of service) attacks last August, forcing trading to be halted on four consecutive days.