A "tubular-shaped" UFO with an S-shaped fin has been captured on film above a medieval castle in the Netherlands.

The strange pictures were taken by Corinne Federer at Muiderslot Castle.

Speaking to HuffPost US, Federer said that she was only able to capture the image because she was shooting a five-frame HDR exposure at the time.

"We heard nothing, it was completely quiet out," she said. "The more I flipped through the frames, it was kind of creepy."

The pictures appear to show the object with an s-shaped fin which flips around as the object moves across the frame.

HuffPost UK contacted a UFO expert at the SyFy channel who said that there was no obvious evidence the pictures were tampered with.

But he did unfortunately have another explanation for the hyper-speed alien missile spacecraft.

"If I had to place my money on it, I would say that we're looking at insects," he said. "We typically see many wing protrusions on insect rod cases, but they do come in the single pair variety, too. It all depends on the shutter speeds and motion of the insects."

For more on this story head to HuffPost Weird News.

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  • Muiderslot Castle UFO - 1

    Faster than the eye could follow, an unusual-looking object was accidentally photographed on May 25, 2013, in the sky above the medieval 13th century Muiderslot Castle in the Netherlands. Corinne Federer took five simultaneous shots (within one second), and two of the exposures revealed what appears to be a tubular-shaped object with a large S-shaped fin, travelling at almost supersonic speed. This first-of-five images was two stops underexposed, and doesn't yet show the UFO.

  • Muiderslot Castle UFO - 2

    In this second-of-five images, the UFO is still not visible in this second-of-five images. This image is one stop-underexposed in a sequence that snapped five pictures within one second.

  • Muiderslot Castle UFO - 3a

    In this normal exposure image, suddenly an unknown object appears in the sky above the castle. The next slide shows the same picture, but with some adjustments made to show more details of the object.

  • Muiderslot Castle UFO - 3b

    In this image, the contrast and gray scale settings of the original exposures have been adjusted to further clarify the unexplained object that was photographed by Corinne Federer over the Muiderslot Castle in the Netherlands on May 25, 2013.

  • Muiderslot Castle UFO - 4a

    This is a plus-one exposure of the one-second, five-image sequence that now shows the unexplained object on the far left of the screen. Because the UFO can barely be seen, adjustments were made in the contrast to bring more clarity to it in the next slide.

  • Muiderslot Castle UFO - 4b

    This monochrome version of the preceding slide, with blacks and shadows maximized to bring out details in the image, shows the UFO more clearly on the far left of the screen. The next slide shows a closer view of the object.

  • Muiderslot Castle UFO - 4c

    This slide shows two enlargements of the object that appeared at the extreme left side of the five-image sequence.

  • Muiderslot Castle UFO - 5

    This is an overexposed, final shot of the five-image, one-second exposure of the unusual aerial object above the Muiderslot Castle. The object is gone from this image. Former FBI special agent Ben Hansen analyzed the full exposure sequence and strongly suggested that the rapidly moving objects were most likely insects, flying so fast that they were only picked up on two of the five images.

  • Muiderslot Castle UFO - Higher UFO In The Sky

    While former FBI special agent Ben Hansen was studying the five-image sequence of the Muiderslot Castle UFO, he noticed something else, much higher in the sky that could barely be noticed upon first glance. In this image (which was the second-of-five), the red circle surrounds another object. The next slide brings it much closer in view.

  • Muiderslot Castle UFO - Higher UFO In The Sky Closer View

    The image on the right is an extreme close-up of what the red circle is surrounding in the left image. This object was noticed by Ben Hansen, lead investigator of the Syfy Channel's "Fact or Fake: Paranormal Files," while he studied the entire five-image sequence that were taken in the span of one second. Hansen asserts that the alleged UFOs in these images were probably insects.