Hello @David6564
Sorry to hear this.
What did your guests say when you called them about this?
Do message them through Airbnb to follow up in writing to tell them that any guests they have invited onto the property who haven't booked and paid must leave immediately.
Phone Airbnb and ask them to cancel. They will probably say they have to reach out to the guest (who probably won't answer). Make sure you send them photos and videos from your listing surveillance camera's so they can see the party in action.
Get yourself over there with a couple of beefy friends asap, so you can be on hand to make sure the party guests leave. Hopefully by that time, airbnb will have cancelled the booking and you can evict the paying guests too.
Record the state of the property with video and photos in case you need to submit a claim.
I would add to your house rules that the listing is for accommodation only and only those who have booked and paid should be on the premises. Also add those wanting to use it for an events need to inquire with you for details and pricing separately at an additional cost.