How to delete all photos in Lightroom Mobile?

I would like to delete all of the photos in my Lightroom Mobile photo library. A one-step procedure would be ideal.

For background: My Lightroom desktop catalog has tens of thousands of photos and hundreds of collections. When I was first getting familiar with Lightroom Mobile, I synced all of my photos with the service. This was a mistake; I did not realize that this would result in large amounts of data filling up my mobile devices (I thought the service worked more like Dropbox, OneDrive, etc., where photos are loaded as-needed). My Lightroom Mobile photo library is now much too large to fit on my mobile device, and even partially syncing fills up my devices immediately. I want to clear out my library and start over.

Individually selecting each image in the web interface is not a practical solution. It is also not practical to keep all of the photos in Lightroom mobile and then delete unwanted collections from individual mobile devices, since this would involve deleting hundreds of events from each mobile device each time I set up Lightroom Mobile. I would like to clear my library and start over with a small number of synced collections.

Any advice on how this could be done would be appreciated!