A woman has been arrested after the burning of an Australian flag at the Anzac War Memorial in Sydney's Hyde Park.

Emergency services were called to the park on Wednesday afternoon after a flag was allegedly removed from the memorial and burned in its flame of remembrance.

A member of the public contacted police after CCTV footage was released, and officers arrested a 36-year-old woman at Central Railway Station in the early hours of Thursday.

She was being questioned at Sydney City Police Station.

Minister for Veterans Affairs Victor Dominello and RSL NSW President Don Rowe on Wednesday condemned the incident.

"Not only is this criminal behaviour, its deeply disrespectful of the memorial and all it represents," Mr Dominello said in a statement.

"It is deeply concerning that any person would seek to desecrate the Australian flag.

"Doing so on this sacred site makes it all the more reprehensible."

Mr Rowe urged members of the public to come forward with information.

"Veterans and their families will be outraged by this attack on a sacred monument dedicated to thousands of Australians who have fought and died for their country," he said."

The woman has since been taken to St Vincent's Hospital, where she is being assessed.

Police say a decision will be made on the direction of their inquiry once this is done.