iPhone virus attack?

I recently watched a video in a website using safari. The video became frozen right away after I clicked on the link. I removed the tab and was able to watch it after reloading the video. However, I was alerted with this sort of message (sorry, I cannot recall the exact alert) “Your iPhone has been attacked by 39 viruses. You need to install antivirus app from App Store. In xx minutes and xx seconds (the timer is changing), you may be able to clear the virus.” Both antivirus app and clear words seem to be clickable. Is my iPhone really attacked by viruses? How can I remove the viruses? Thanks for your support!