Police in Germany are investigating after a Berlin auction house was prevented from selling three landscapes that were apparently signed by Hitler.

Questions have been raised over the authenticity of paintings supposedly made by the Nazi dictator.

As many as 30 artworks carrying prices up to tens of thousands of euros are under suspicion, The Times reported.

The auction house in question, Weidler, has reportedly sold more than 100 paintings in the last five years carrying the designation “Hitler”.

It describes such paintings as “signed or monogrammed by A. Hitler (prob. Adolf Hitler 1889 to 1945)”.

Kerstin Weidler, the auctioneer, told the newspaper that to suggest the pictures were fake was “an unfounded claim. There are different points of view and we as an auction house must remain neutral in this whole subjectivity.”

Since 1945, hundreds of artworks purportedly created by Hitler have been sold.

Prior to the First World War, the future dictator was rejected twice by the Academy of Fine Arts in Vienna.

He wrote in Mein Kampf, his autobiography, that while living in Vienna he had produced around two or three paintings a day. Many were watercolour replicas of postcards.

Given that Hitler spent six years in the Austrian capital, that could amount to several thousand works — although it is entirely possible he was exaggerating his productivity.

Nazi attempts between 1933 and 1945 to trace all paintings reliably created by their leader only resulted in a few dozen works being catalogued.

“He didn’t have a clue about perspective and was very bad at painting people, so any painting that includes many people is very unlikely to be authentic,” investigative journalist Bart Droog told The Times.