Two people are dead after a petrol tanker crashed and exploded at Mona Vale on Sydney's northern beaches.

Emergency crews are at the scene on Mona Vale Road after the crash about 3:40pm (AEST).

Police say the fuel tanker caught alight as a result of the multi-vehicle collision.

A number of buildings near the site at the intersection of Samuel Street have been evacuated as a precaution.

Mona Vale Road has been closed near the crash site and motorists are being urged to avoid the area.