"Alert! You have a security problem!" Pop up?

I'm gettign these really annoying pop ups, one says 'Alert! You have a security problem! Do you want to scan your computer for viruses?', it also usually appears with two other full screen pop ups with fake scanners and things, I think they have something like tube-funs-worlds.com and promotion.com/ and something like fghhfhhg.com in the url. ( I no that last one isnt right but the url is just a random bunch of 'f's 'g's and 'h's as far as i no.) I have Malwarebytes' Anti malware and AVG installed but neither is doing anything about it.
What is this and how do i remove it?
thank you xx