A Dutch retailer has been forced to apologise after it unwittingly sold a colour-by-numbers book featuring Adolf Hitler.

The dictator was pictured making a Nazi salute and wearing a Swastika armband.

Kruidvat, the Dutch drugstore chain stocking it, said they "deeply regretted the incident" and immediately withdrew the product.

The book was produced in India and it is remains unclear why Hitler was included.

"My suspicion is that the man who created the colouring book got a book of famous people out of the closet and selected a pair, which unfortunately included Adolf Hitler. Maybe he did not recognize him," a spokesperson for the Belgian publisher Trifora told local media.

The publisher explained the book, Kleuren op Code, included significant historical figures such as Nelson Mandela, Albert Einstein and Abraham Lincoln.

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"It is a nasty combination of circumstances. We check the book on translations, but do not check all the colouring pictures," the spokesperson said.

The Dutch retailer was only alerted after the book had gone on sale and shocked parents began posting comments on social media.

One parent posted an image of the page with the caption: "Nice, your colouring book!"

Another customer called it a "disgrace" on the company's Facebook page.

Kruidvat said it was only on sale for half a day and was immediately removed from shelves when the problem came to light.

The company said it was investigating how the image ended up in the book and was offering full refunds to customers who bought copies.