All commercial and civilian aircraft in New Zealand were grounded on Tuesday due to a fault in the South Pacific nation's air traffic control system, an official said.

Airways New Zealand, which manages air traffic control, said all flights, including international and domestic services, were affected.

A spokeswoman for the government agency said technicians were working to find the cause of the problem but it was impossible to say when it would be fixed.

"There has been a radar failure that has occurred at 2.48pm (0248 GMT) this afternoon, we are working on the issue at the moment," she told AFP.

"The impact is that all aircraft have been held on the ground. There are no aircraft taking off across the country. The aircraft that are in the air have been cleared to land."

Airways NZ's website says it manages 30 million square kilometres (nearly 12 million square miles) of airspace, handling about one million aircraft movements annually.

Auckland airport, the country's largest, warned travellers to expect delays.