A large screen in downtown Cardiff was hacked by some pranks who showed offensive images including Nazi and Islamic law.
The huge digital billboard, located next to a building on the main shopping street in the Welsh capital, had to be closed after being taken over on Tuesday night.
A picture flashed on the screen shows: "Warning.
This is an area controlled by Islamic law. No alcohol. No gambling. No porn.
Another cartoon shows the frog Pepe the frog played by Donald Trump-a character that has increasingly become a symbol of "alternative"
The right political movement.
Tweets related to the internet prank message board 4 chan initially drew attention to the incident.
The account was released: "some anonymous people from/pol/were able to hack into billboards in Cardiff, Wales.
As you can see, they have a good time.
The bombing Media, which controls billboards, has reached out for comment.
South Wales Police said in a statement: "on Tuesday night, South Wales Police received a number of phone calls concerning concerns about information displayed on the Cardiff Queen Street screen.
"We have alerted the city council and will investigate any crimes that may have been committed.