San Francisco has painted nine walls with a repellent material that makes pee spray back off them in a bid to tackle public urination.

The walls have been coated with the clear liquid repellent material, which goes on much like paint. Any urine that hits the material sprays back on a person's shoes and trousers.

Mohammed Nuru is director of the city's public works department and calls himself Mr Clean.

He got the idea from St Pauli quarter in Hamburg, Germany, where walls are painted with the clear material to discourage late-night beer drinkers from urinating in alleyways.

It is San Francisco's latest effort in its battle against public urination.

The city also has solar-powered rolling toilets in one neighbourhood and attendants manning public toilets to encourage people to use them.