A Nazi sign has been sprayed on a famous monument to a flooded Welsh village.
Police have been made aware of the swastika on the Cofiwch Dryweryn wall.
And local MS Elin Jones said: "This is not a prank - it is sinister and dangerous."
The painted message 'Cofiwch Dryweryn' (Remember Tryweryn) – a reference to the Welsh village that was flooded to provide water for Liverpool – was first daubed on a derelict wall at the side of the A487, overlooking Llanrhystud in Ceredigion, in the early 1960s after the failure of a campaign to prevent the flooding.
The graffiti has since become an unofficial national landmark.
For years campaigners have fought to save the wall which is situated around nine miles south of Aberystwyth.
In the past, vandals painted over with the word 'Elvis'.
Then, a group of locals who felt passionately about it repainted it in the middle of the night.
Anyone with information about the latest attack is asked to contact police at Dyfed Powys Police on 101.
