New Zealand police raided what they called military-style training camps and private homes on Monday, seizing firearms and arresting 17 people from domestic groups on arms and possible terrorism offences, authorities said.

More than 300 officers took part in the raids in several parts of North Island and in the southern city of Christchurch, which followed reports to police of camps being used to train people to use a variety of weapons.

"They are training in the use of firearms and other weapons. These are military-style activities that they were training for," Police Commissioner Howard Broad told reporters. "I believe this is domestically oriented, I don't have evidence there is an international connection to this."

The groups involved were drawn from "various ethnicities" and had "a variety of motivations," Broad said.

The arrests appeared aimed primarily at environmental protest groups and Maori sovereignty activists. The Maori are a Polynesian people who make up 15 per cent of New Zealand's four million population.

Police anti-terror chief and acting deputy commissioner Jon White said that while there was "not necessarily" indications of an imminent terror attack, the training camps "appeared to be involved in activities which were unlawful."

White declined to elaborate further, saying the issues were now before the courts.

Some fringe Maori groups claim New Zealand's 540,000 Maori should be granted self-determination and have ancestral lands confiscated in the 19th century returned to their tribes.

Environmental groups in recent months have invaded coal-fired power stations to draw attention to their greenhouse gas emissions. One group had members cement themselves to a rail line used to transport coal from a company it claims is endangering a giant native snail.

Broad said a number of firearms had been found in the raids.

Police spokeswoman Jane Archibald told the Associated Press the 17 people arrested, including four women, would appear in district courts on firearms charges.

In the capital, Wellington, two men and two women appeared in court on weapons changes, including illegal possession of military-style firearms and molotov cocktails. They were ordered to remain in custody. Their names and other details weren't released by the court.

Further arrests were possible, Archibald said, with inquiries continuing in some areas.