It is understood the five graffitied prints were behind glass. They were earlier removed from display for restoration, after protesters attacked them.

Police are investigating the incident, but no arrests have been made as of Wednesday afternoon.

The Canberra institution has declined to make any comment, including on the state of the artwork, other than confirming it is the latest gallery to be targeted following similar incidents elsewhere in Australia and overseas.

"The National Gallery does not wish to promote these actions," it said in a statement.

The anti fossil fuel protesters had attempted to glue their hands to the famous Campbell's Soup Cans, before the demonstration was disrupted by staff.

It is understood security staff acted quickly enough to remove the protesters' hands before the glue had time to set.

The gallery was reportedly on high alert following demonstrations around the world, including at London's National Gallery and the Uffizi Gallery in Florence.

Two men glued their hands to paintings - including the glass covering to Johannes Vermeer's Girl with a Pearl Earring - in Mauritshuis gallery in the Hague late last month.

Others threw tomato soup at Vincent van Gogh's Sunflowers at the UK's National Gallery. Mashed potatoes were thrown at Claude Monet's Meules in Germany.

Andy Warhol's famous Campbell's Soup Cans was targeted in Canberra as the American pop artist depicted "capitalism gone mad" in his work, the group responsible said.

Protester Bonnie Cassen said she graffitied the artwork at the National Gallery of Australia to draw attention to subsidies to the fossil fuel industry.

"Families are having to choose between medicine and food for their children while fossil fuel companies return record profits," she said in a statement.

"And yet our government gives $22,000 a minute in subsidies to the fossil fuel industry.

"This is despite having pledged at last year's COP27 to phase out inefficient fossil fuel subsidies."

Stop Fossil Fuel Subsidies is part of a global network called the A22 Network, which has been using art disruption tactics over the past few weeks.

Last week one of their protesters glued themselves to the Suffragette's Exhibition at Parliament House.

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Ms Cassen, a mother of three who says she is battling an incurable cancer, said the latest IPCC report revealed the planet was already at 1.5 degrees of warming.

"We must act urgently to avoid the worst effects of climate breakdown and large-scale extinctions," she said.

"Is art really more important than human life?

"I am spending my remaining days living with incurable cancer fighting to protect the planet.

"We only have a limited time. I need people to stand up and join me."

The protectors are believed to have left prior to police responding to the incident at 11.15am.

The institution, which hosted the announcement of the ACT Australian of the Year Awards on Wednesday, had barred photographers from entering the gallery area.

ACT police have confirmed an investigation is now underway.

"About 11.15am today, ACT Policing responded to reports of an incident involving two people at the National Gallery of Australia," they said

"At this time, no arrests have been made."

ACT Policing asked anyone who witnesses suspicious activity in the Parliamentary Triangle to call ACT Policing Operations on 131 444.