UPDATED 2.29PM A police officer is alleged to have fatally shot his female partner and a man in the Anzac Day double shooting in Invercargill.

Just after 8pm on Otepuni Ave, Newfield, witnesses said, a man pulled up outside the house in question and began shooting.

Today, a source has told the Herald the shooter was an off-duty policeman.

However, a New Zealand police spokesman said he was unable to confirm the alleged shooter was an officer.

"There is a legal process we need to work through before we are in a position to comment any further," police said in a statement.

Police today confirmed a woman died in the shooting. The second victim was last night in hospital with serious injuries.

One person was in custody and helping with the investigation. No one else was being sought in relation to the shooting.

The witness, who saw a man pull up on his bike in what's been described as a largely industrial area, said there were "cops everywhere".

He saw police with torches searching an area outside the commercial building.

Local Terry Brown said he saw a "chap" bike past, and had an inkling something was off.

"It didn't look right. It looked a bit suspicious," he said.

His interest was piqued when the man took off the top he was wearing and put on another, darker piece of clothing before cycling down Otepuni Ave.

Within half an hour the cyclist rode back past his house, still wearing the dark clothing.

This morning the street remained closed.

-NZ Herald