Nelson police have the backing of the city's mayor as they try to keep a lid on gang tensions this weekend.

The city's resident gang, the Southern Skinheads, have threatened to shoot Hells Angels members if they turn up for today's charity bike rally. They have also mentioned setting fire to motels the gang stays at and bars they drink at.

Police are vowing to keep to a close watch on the bike run and say locals should not be intimidated, but Mayor Kerry Marshall says threats of shootings and violence have put some people on edge.

"I think it's a ridiculous statement by those people quite frankly but it does scare people and we're concerned about that, so I've got great faith in the Nelson police. We'll just keep our fingers crossed that nothing stupid happens."

Mr Marshall hopes the threats prove to be empty.

"There has been quite a lot of publicity and I think people will be very, very careful and cautious. I get the impression notwithstanding those threats that were made that hopefully they will come and do their thing and go."