"Sick and disgusting" far-right graffiti has been daubed on buildings in one of Cardiff's most culturally diverse communities.
Swastikas, the slogan "Nazi Zone" and offensive posters were spotted by parents on the school run in Grangetown.
Greg Pycroft, who tweeted pictures, said it was a "sad, sorry sight".
Cardiff-council said far right extremism was not welcome in the city, and the material was being removed.
South Wales Police said a full investigation would be carried out and CCTV was being studied.
Mr Pycroft said he saw the graffiti in and around Grange Gardens while on the school run, adding: "Hopefully @cardiffcouncil will be able to remove everything before kids head home this afternoon."
His post generated outrage among members of the community, with Stephen Doughty, MP for Cardiff South and Penarth, tweeting: "Utterly sick + disgusting - will be raising with @swpolice @swpcardiff @cardiffcouncil immediately - far right extremism cannot be tolerated and not welcome in Cardiff. Full stop."
Other people posted to say they were trying to find all the posters and take them down.
Ch Insp Joe Jones, head of communities and partnerships at Cardiff Bay police station, said: "Cardiff is a modern, vibrant and safe multi-cultural city where people of different religions, faiths and cultures live side by side in peaceful harmony and have done for many, many years.
"The vandalism of public buildings with such abhorrent racist graffiti is totally unacceptable criminal behaviour and it will not be tolerated.
"The offensive graffiti is in the process of being removed and there will be a full investigation into this crime with every intention of arresting and prosecuting the perpetrators.
"CCTV and house to house enquiries are already under way and posters recovered at the scene have been sent for forensic examination."
According to the last census, 38% of residents in the Grangetown area are from black, Asian and ethnic minority backgrounds.
Cardiff council said: "We condemn all graffiti in the strongest possible terms and we are working with the South Wales Police on this matter and the offensive graffiti and fly posting will be removed as quickly as possible."
Ash Lister, councillor for Grangetown, said he thought the graffiti came from outside the community and thinks it could be related to an anti-racism march which is due to take place in the city on Saturday.
He said: "I wouldn't say this is something that had come from someone within the Grangetown community, if I'm honest, particularly not considering it's lining the route of the UN Anti-racism march.
"I think this is people that have come into the area, intruders...the community themselves won't tolerate this."