How to delete images without any tag?

[bluepuma77]

We sometimes update images in the registry, so a newer image will get an already used tag, the old image will be left without a tag.

REPOSITORY    TAG       IMAGE ID       CREATED         SIZE
reg:443/app   latest    4e2bace08a25   4 seconds ago   214MB
reg:443/app   9.9.49    4e2bace08a25   4 seconds ago   214MB
reg:443/app   9.9.48    2c4a5c62ce6c   42 hours ago    214MB
reg:443/app   9.9.47    9b3ab1154b85   2 days ago      214MB
reg:443/app   <none>    13ba38c89f33   2 days ago      214MB
reg:443/app   9.9.46    d3949a15fd93   4 days ago      214MB
reg:443/app   <none>    beb24bafaac4   4 days ago      214MB

How can I delete all images without any tag? If it's possible, it would be great to add this case to the examples.