New Zealand police are investigating a series of arson attempts on cell tower sites, with the head of police stating those responsible would be dealt with firmly.

Police Commissioner Andrew Coster said in a press conference on Monday that police were investigating the attacks.

"This is critical infrastructure. These actions are reckless to say the least," Coster said.

There have been at least 15 suspicious attacks or fires at cell towers around the country in recent weeks, industry body Telecommunications Forum said in a statement.

Chief executive Geoff Thorn said the attacks were “highly dangerous” and could disrupt internet and phone service, leaving people unable to make emergency calls.

"The people responsible for these criminal acts are putting New Zealand lives in danger at a time when the country is making sacrifices to rid our communities of a deadly virus," Thorn said.

Thorn said in other countries damage to mobile networks had been linked to groups opposed to 5G.

"There has been comprehensive and ongoing research into this issue and there is no evidence that 5G causes harm," Thorn said.

A video posted to Facebook which has since been removed showed an arson attack in Auckland and included anti-5G statements, the New Zealand Herald reported.

In April, Prime Minister Jacinda Ardern was asked during a press conference about a theory being spread that 5G was linked to Covid-19.

"That is not true. I cannot state that clearly enough," she said.

The World Health Organization has responded to such theories in a Covid-19 "myth buster" that "viruses cannot travel on radio waves/mobile networks”.

 - dpa