Spam iCal invitations: How to deal with them

Hello,

I've received a spam iCal invitation which advertises sales on sunglasses. My only options shown in iCal are "Accept", "Maybe" or "Decline".

Preferably, I'd like to delete the invitation, since choosing any options above will alert the spammer that my E-Mail address is valid. I would also like to get rid of the red (1) on the iCal app icon.

I have so far been unable to find an option on my iPhone which would allow me to "accept iCal invitations from my contacts only" or "mark invitation as spam" or "delete or ignore the invitation". Are the mentioned options available on iCloud.com or otherwise planned for a future release?

I would be delighted if you could foremost help me get rid of the red (1) icon on the iCal app without alerting the spammer.

Thank you very much in advance, I have already reported this incident on abuse@iCloud.com. Below are screenshots of said invitation for further analysis.

Regards,

Ryu