A couple's chance wedding photograph with members of New Zealand's Black Power gang has gone viral on Facebook.

Newlyweds Sarah and Matthew Oke were having their pictures taken at Lucy's Gully on the North Island when they ran into the gang members.

They were in the area paying respects to the dead as part of a traditional Maori "hikoi" at the mountain.

The gang members agreed to pose for a picture with the couple, and even gave a salute.

Formed in Wellington during the 1970s, Black Power is a prominent gang made up of Maori and Polynesian members.

Some members have been linked to drug running and other organised crime.

'Very respectful'

Photographer Rebecca Inns, 31, who captured the moment on film, detailed the experience in a Facebook post.

"The rain had just cleared and we were enjoying a lovely sunny wedding shoot," she described. "As we headed back, we came across a very full car-park and the guys who were there as part of a hikoi."

"We asked if it would be okay to include them in a wedding photo and they were really accommodating. This is the result."

'Random, unplanned and totally unique'

The unconventional photograph received 5,000 reactions on the site and was shared close to 600 times.

Some have praised it for helping to break down barriers and racial stereotypes.

Inns, who said the couple had given her permission to share the photo, told the BBC that she was "completely taken by surprise" at the interest.

"Both parties just happened to be in the same place at the same time, both there for their own special reasons - and it has made for a wonderfully unique photo," she said.

"We definitely did not expect it to go viral when capturing the moment. But we pride ourselves on recording those unique moments in a couple's special day."

Inns said the gang members had been "very respectful".

"They all offered their congratulations to the couple and were so kind. They also told the bride how beautiful she looked."