Police are puzzled by the discovery of three garbage bags full of freshly-cut marijuana with a sign reading "Free dope. Mull up" dumped by a road on the New South Wales south coast.

A local man made the discovery on Bolong Road, near Nowra, on Saturday morning while on his way to go fishing.

Police say the bags contain around 16 kilograms of marijuana with a street value of around $90,000.

Police are appealing for anyone who saw the green bags being dumped to come forward.

They say the cannabis will be destroyed.