Pop up “update error1” message (virus? Or real?)

hello everyone,

Ive recently been getting this error message appear on my iphone 6s

The screen will go dark and the words “update error1” with the options Accept or Cancel on the bottom of screen and back in the top left.

See attached photo.

I’ve never seen this sort of notification before and seems a bit suspicious to me.

Any advice on what I should do.