The graves of Australian war veterans have been spray painted blue at Harefield cemetery in London on the weekend.

The site houses the graves of 126 Diggers, who mostly died at the nearby No.1 Australian Auxiliary Hospital after being wounded on the Western Front during the first World War.

About a quarter of the headstones, refurbished earlier in 2015 in time for Anzac Day, were vandalised, reported the ABC.

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War Graves Commission official Peter Francis labelled the graffiti a “sickening act” and “deeply distressing”, reported Weekly Times Now.

A police investigation into the incident was launched and an expert clean-up team was called to the scene.

Mr Francis said the vandals did not appear to have specifically attacked Australian graves, nor did there seem to be any explicit message in the graffiti.

“Obviously it’s someone who just doesn’t appreciate what these people did for us. It looks like just a mindless act of vandalism, just pure stupidity,” he said.

Mr Francis said high pressure water hoses would be used and would hopefully be able to remove the paint.

It’s not the first act of vandalism at the war cemetery this year, after a flag pole was cut in half and a newly renovated information panel was spray painted earlier in 2015.