Hundreds of shoppers were evacuated from Hobart's Northgate Shopping Centre after an air-conditioning unit caught fire.

 Police diverted traffic around the shopping centre, shops were evacuated and the power switched off after smoke was reported about 10.30am.

 Two fire trucks attended the scene. Fire authorities later said a fire in an airconditioning unit had pumped smoke into the centre.

Police allowed shoppers and business owners back into the centre after about an hour.