More than a dozen New Zealand schools received bomb threats on Thursday, which caused widespread disruption, with authorities denouncing a cyberattack orchestrated from abroad.

Most of the schools affected have been closed or evacuated.

Cherie Taylor-Patel, president of the Federation of Head Teachers of New Zealand, told RNZ radio that she had spoken to the Department of Education, who “understand that it was in fact 'a cyberbot from abroad'.

New Zealand Police said in a statement that they "do not believe there is a security risk".

This new wave of threats came 24 hours after false calls Wednesday targeting four New Zealand schools, in Waikato, Thames and Gisborne (north).

Authorities said they were still investigating threats to schools in Marlborough, Masterton, Kaikoura, Greymouth, Queenstown, Levin, Whanganui, Rolleston, Takaka, Geraldine, Dunstan, Ashburton and Palmerston North.

Tasman Area Commander Simon Feltham said they were questioning 'two young people' about a threat to Marlborough Girls' College.

No explosive device was found in the targeted schools.

Schools in New Zealand and Australia were targeted by bomb threats in 2016.

In 2018, an Israeli-American was sentenced to 10 years in prison by an Israeli court for issuing around 2,000 false alarms in North America, Britain, Australia, New Zealand, Norway and Denmark.