A group of anonymous bike activists have embarked on a guerilla campaign, plastering roads across Sydney with the slogan "Unsafe cycle lane".

The message has been painted dozens of times on bike lanes, including on Moore Park Road and Greens Road in Paddington and Doncaster Avenue in Kingsford.

The cyclists are believed to be protesting against unseparated bike paths, such as this one, which are between parked cars and the main road. Credit:David Quick

The campaign appears to have been well organised with the slogans seemingly made from stencils and colour co-ordinated to match the paint already on each lane.

The targeted roads have unseparated bike lanes, where strips of paint, rather than a physical barrier, demarcate a bike lane between parked cars and the main road.