Can articles published to Apple News in Apple Native Format (ANF) include images from a URL?

Question

I am creating Apple Native Format (ANF) documents to upload to Apple News. The examples in the documentation upload images in a "bundle", along with the requisite article.json file. These images are then referred to via a Bundle URL, e.g.:

{
  "role": "photo",
  "URL": "bundle://summer.jpg",
  "caption": "Thanks to the record drought...."
}

Is it possible to use a URL to an image on the internet, e.g.:

{
  "role": "photo",
  "URL": "http://some.cdn.com/adsf8765a/summer.jpg",
  "caption": "Thanks to the record drought...."
}

I would have thought so, but the articles I have uploaded thus far to our Sandbox account refuse to display any image that isn't bundled. These images DO conform to the required specifications.

What am I doing wrong? Or is it simply not possible?

UPDATE: (6/12/2015)

An official reply from Apple confirms the answer below.

We do not currently support remote urls for images, though it is an existing enhancement request that we are considering for the future.

Answer 1

Update: 19/05/2017

Referring to images by URL is now possible.

Image URLs can begin with http://, https://, or bundle://. If the image URL begins with bundle://, the referenced image file must be in the same directory as the document.

Source: Apple News Format Reference

I'm not sure when this first became available, but we've been using it since mid-2016.

Answer 2

Short answer, no, you need to use the bundle url and attach all the required images. At least we never found a way to specify an external URL.

According to the docs (0.9 draft):

For use in the Preview Tool, image URLs must begin with bundle:// and must refer to images in the same directory as the document. Image file names should be properly encoded as URLs. For example, spaces in a URL should be encoded as %20. Images used with the Preview Tool should be no more than 20 MB, and height and width should not exceed 6000 pixels.

but in my experience this extends to content published in channels too.