SYDNEY, Sept 8 (Reuters) - Websites of a number of financial institutions in New Zealand and its national postal service were briefly down on Wednesday, with officials saying they were battling a cyber attack. The country"s Computer Emergency Response Team (CERT) said it was aware of a DDoS (distributed denial of service) attack targeting a number of organisations in the country. It was "monitoring the situation and are working with affected parties where we can," CERT said on its website. Some of the affected websites affected by the attack according to local media reports included Australia and New Zealand Banking Group"s (ANZ.AX) New Zealand site and NZ Post. In a Facebook post, ANZ told customers it was aware some of them were not able to access online banking services. "Our tech team are working hard to get this fixed, we apologise for any inconvenience this may cause," the post said. Representatives for ANZ did not immediately return requests for comment. NZ Post said the "intermittent disruptions" on its website were due to an issue at one of its third-party suppliers. Several customers resorted to social media to report outages at Kiwibank, a small lender partly owned by the NZ Post. Kiwibank apologised to customers in a Twitter post and said it was working to fix "intermittent access" to services in its app, internet banking, phone banking and website. In DDoS attacks, the servers of high-profile institutions are crowded out by incoming traffic from superfluous requests that try to overload the system and drown legitimate requests. In January, a cyber-attack led to a serious data breach at New Zealand central bank, which followed several attacks on the operator of New Zealand"s stock exchange a year ago. A group of hackers also targeted hospitals in May. read more