One of Adelaide's most iconic landmarks has been vandalised, as part of a brazen spate of graffiti in the city's retail centre.

Two local painters spent Sunday morning cleaning graffiti from the Mall's Balls in Rundle Mall, after an unknown assailant tagged the sculpture overnight.

Shop fronts and walls along Gawler Place not far from the steel sculpture were also targeted.

Photos of the vandalism were posted on social media this morning.

Cleaners wiping off graffiti from Adelaide's iconic Mall's Balls that were vandalised overnight. ( ABC News )

The social media account also posted video of what appears to be a man spray-painting a wall in Gawler Place.

The council says there's unlikely to be any lasting damage to the work, and police will be investigating the incident.

The Mall's Balls — officially named 'Spheres' — feature prominently in marketing for the city of Adelaide, and are a tourist drawcard.

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Bert Flugelman's artwork has been in Adelaide since 1977 and features prominently in marketing for the city.

He is also known for other silver sculptures including Slow Spiral, on display in Brisbane, Cones in the sculpture garden of the National Gallery in Canberra and Pyramid Tower in Sydney, known by many as the silver shish kebab.

The Austrian-born visual artist died in 2013.

Spheres was donated to the city by the Hindmarsh Building Society, to mark the society's centenary.

It's the second time the sculpture has been at the centre of late-night drama in six months, after police condemned the actions of a man who leapt on top of the Mall's Balls from a nearby canopy.

A Kudla man pulled a similar stunt in 2013.