Q: Virus or a scam???

Mistyped a website and got a pop up and audio alert. Pop up stated "http://computer-attention-alert.com DO NOT SHUT DOWN OR RESTART COMPUTER call toll free number" ; audio alert said "do not make any purchases on this computer, your computer has a virus." Would not let me leave the page so I force quit Safari. ??? Is this legit or do I really have a problem??? Now afraid to enter my credit card info since the voice told me not to Thanks for any input!!!