A heavy police presence protected the forum, at the TSB Bank Arena in Wellington. Peace Action Wellington claimed officers were heavy-handed in their response to the protesters.

Police have made 24 arrests during clashes outside the New Zealand Defence Industry Association annual forum at the TSB Arena in Wellington on Tuesday.

Amid a heavy police and security presence, protesters jeered delegates and attempted to disrupt what they called a "weapons conference".

Inspector Terry van Dillen said nine of arrests were for disorderly behaviour, five for obstruction and two for assault on police.

KEVIN STENT/STUFF A Peace Action Wellington protester is arrested outside TSB Arena where the New Zealand Defence Industry Association is holding its annual forum.

A further eight were arrested for trespass as they were occupying an area of private property at one side of the entrance to the stadium, over which police had "trespass authority", van Dillen said.

Other areas of the entrance to the Wellington City Council-owned arena were deemed public property.

Most have been charged and released, with bail conditions that include not going within 100 metres of the arena when the conference resumes on Wednesday.

MONIQUE FORD/ FAIRFAX NZ Protesters bang on the walls outside the annual Defence Industry Association gathering.

About 150 protesters gathered at the entrance to the arena to voice their opposition to the forum, which links businesses and government agencies.

A witness at the scene said scuffles had broken out between protesters and police protecting forum delegates.

Protester Brenda Crooks said police appeared to be using "heavy-handed" tactics.

"I am protesting because I stand on the side of the people who are dying for the profit of these weapons manufacturers," she said.

Protesters continued to disrupt the forum by banging loudly on exterior doors and walls. The din could be heard clearly in the main speaking area.

Echoing the sentiments of many, city councillor Iona Pannett joined protesters and said it was repugnant that Wellington was hosting weapons makers, including Lockheed Martin, a nuclear weapons manufacturer and the forum's primary sponsor.

"Weapons are not a commodity like any other. They are selling death and destruction – the cycle of violence needs to stop," Pannett said.

Peace Action Wellington spokesman James Barber said many of the arrests seemed random and that protesters were united in their disgust for the arms industry, which seemed to be growing in New Zealand.

The group says the weapons and military-related industry is not legitimate and it was unethical to "cash in on murder and maiming".

Defence Minister Gerry Brownlee said he had no concerns "whatsoever" about the conference, or where it was being held.

"I think you've got to have a look at what sort of conference it was. These are suppliers to the New Zealand Defence Force, so they supply everything from paper cups to socks.

"The Defence Industry Council has existed since 1992 and they're mainly people who supply all the day-to-day needs of military procurement, so that's things like uniforms, daily rations, that type of thing."

Asked whether the suppliers would be offering arms and weapons as well, Brownlee said: "Not as far as I know. Most of those things are very big purchases that are put through Cabinet etc."

While Lockheed Martin was involved in the US nuclear industry, it was "also a systems provider for all sorts of things" in New Zealand and other countries, he said.

"They have, for example, I think they're doing the refit on the frigate engines and that type of thing, so it's not a weapons-based conference at all."

Former brigadier Charles Lott, who still works for the Defence Force as a civilian, spoke inside the forum before it was made off-limits to media, and Secretary of Defence Helene Quilter addressed the delegates.

Lott said about 60 per cent the NZDF's $2 billion defence budget was spent in New Zealand.

"Essentially, the Defence Force runs its own small shipping line, a large trucking company and international logistics firm, a small airline, a small police force, a mid-sized security firm, and an army."

It was "small and agile" and able to embed change quicker than larger armed forces.

"In our business there are no prizes for second place – if you're second place, you've lost."