A painting hanging on a wall of Kilkenny Castle containing Nazi and religious imagery was spattered with red paint, while a photograph of a child displayed in Irishtown, also in Kilkenny city, was set alight.

Both incidents happened early yesterday, and gardaí have appealed for witnesses to the attacks to contact them.

The painting on Kilkenny Castle was not badly damaged and is still in position. Titled The Adoration of the Magi, it depicts uniformed Nazis staring at a Madonna-like figure and child. It is a reworking of a photograph of Adolf Hitler taken shortly before his death.

However, serious damage was done to the image hanging in Irishtown and it has been removed. It was one of nine photographs of local children taken by Mr Helnwein and displayed for the duration of the festival, which ends tomorrow.

A spokesman for the festival said they were "disappointed and saddened" that the images had been attacked. He said Mr Helnwein's work had provoked a strong reaction throughout the festival. "There have been a lot of positive comments but there has been negative reaction as well."

The images have been a major talking point since before the festival began. A former mayor of the city, Mr Paul Cuddihy, initially objected to a painting being hung on the City Hall for fear it might be misinterpreted as lending support to Nazism. After meeting Mr Helnwein at his studio near Clonmel, Co Tipperary, however, Mr Cuddihy said the artist's work was "astonishingly good".

Kilkenny Arts Festival said the artist had a long and acknowledged record of taking a firm stand against Nazism and fascism.