Suspicious Facebook login requirement

Has anyone ever seen this requirement upon trying to log in to their Facebook account?

Facebook message

The message:

Confirm Your Identity

To continue, we need you to provide your mobile phone number. This quick security check helps keep Facebook a community of real people who connect and share using their real identities. If you ever lose your password, you’ll also be able to use your mobile number to access your account.

Confirm your identity by adding a mobile number to your account

Add your phone [Link]

Now, is it just me or is this fishy?

1. As far as I recall, I haven’t given Facebook my mobile number. So they’re not asking for it to validate against their records. (And if they were, wouldn’t they make that clear?)

2. As far as I know, there’s nothing that prompted this. I haven’t changed my email address, my name, or used my account unusually. If they are doing this “for my protection” (i.e. if my account has been hacked) they certainly aren’t being upfront about that.

3. They have literally locked out my account until I provide this information. I can’t get past this screen, nor can I access via any mobile access. (In fact, on a mobile site, it tells me my account is locked and that I must visit the site on a computer.)

Anyone have any insight into this rather suspect development?