Respected actor Sam Neill has fired a broadside at politicians using the Anzac legacy as a justification for going to war, in an exclusive interview with the Sunday Star-Times.

It comes as Australian police say they have halted an ISIS-inspired terror attack planned for Anzac Day.

Sevdet Besim, 18, appeared in court yesterday, one of five teens charged as Australian authorities vowed to step up security ahead of Anzac Day commemorations.

Prime Minister John Key plans to discuss the terror threat with his Australian counterpart Tony Abbott when he visits Wellington tomorrow .

The Australian Prime Minister urged Australians not to be deterred from attending Anzac Day commemorations out of fear. And earlier yesterday, Key joined more than 500 people to attend the official opening of the Pukeahu National War Memorial Park in Wellington.

RSA chief executive David Moger has also reassured New Zealanders, saying there will be a heavy police and military presence at Anzac Day services.

He had not heard of any specific threats against commemorations in New Zealand, but

he country could not afford to let its guard down. "If the Police do advise of an alert then clearly we will take full notice."

On the eve of New Zealand force's departure for Iraq, Neill said New Zealanders should "be cautious when you hear politicians use the word Anzac".

Neill made the comments ahead of Maori Television's screening of his new documentary Anzac: Tides of Blood, which traces his family's military history.

"One of the points we make is that [Anzac] is easily manipulated," Neill said.

"When we are being pushed into conflicts where it may not be wise to enter, invoking the spirit of Anzac you have to exercise a healthy size of scepticism when you hear the word."

Neill questioned the decision to return Australian and New Zealand to Iraq to train the Iraqi army against Islamic State. "It seems amazing that we are going back to Iraq. That is a very big decision to make.

"You can say it is 100 men. It is not 100 men, it is the country (that) is committed to going back to Iraq. There is almost no debate about it. This is a really critical decision. I don't know if it is the right thing to do but I think we should be debating it. I think there should be a really thorough debate."

* Teens arrested in terror raid WORLD p14