A Northland school is one of at least four around the country to receive a hoax bomb threat phone call today.

Whangarei Primary School got the automated phone call about 11.20am, along with schools in Auckland and one in Tauranga.

Whangarei police were notified and said the automated message kept repeating and referred to a threat to the school involving a bomb.

It is similar to those calls sent to schools around the country last month.

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At that time a computer forensic expert was warning an underground group of cyber teens bent on causing mayhem could be behind the spate of hoax bomb threats causing havoc in New Zealand schools.

Special Tactics managing director Daniel Ayers warned authorities to brace for more bogus bomb scares as a group operating on the dark web known as "evacuators" target schools to bring about as much chaos as possible.

Mr Ayers said the group was spreading its reach internationally through an online appeal for teenagers to nominate their schools for "swatting", a term used for making a false complaint that leads to high level police response.

In one week, there were at least 33 primary, secondary and intermediate schools forced into lockdown after malicious calls were made to principals threatening live bombs in schoolyards across the country.

In each case, the call appears to have been made locally using voice over internet technology (VoIP) that converts international calls into local phone calls. Mr Ayers said it was important for the loophole to be closed at a Government level.