“Your system is infected with (16) Viruses” when closing a Safari

I got this message when I was trying to close an earlier window, in the Safari browser. Suddenly I get a pop-up notification, I try hit cancel, but then another pop-up message gets in the way. I have no idea what I pressed but now I got that message and it says I have 5 minutes to get rid of the virus. It didn’t ask for any of my information and I haven’t given any.

Should I be worried?