Part of State Highway 1 in Wellington is closed because of a bush fire.

The blaze broke out on Takapu Rd in Grenada North at about 4pm.

NZTA has closed the southbound Tawa off-ramp and has advised motorists to avoid the area or delay travel.

People working in nearby businesses helped raise the alarm.

David Laurenson said he called emergency services just before 4pm.

He said he could still see flames and a lot of smoke.

Police have been called to the scene to assist with traffic management.

Fire services are also at the scene.

A spokesperson said there were currently around eight appliances plus the rural fire service at the scene. A helicopter had also been requested to help.

He said they were getting on top of the blaze.