A graffiti vandal has been plastering buildings and street fittings in Oxford with the word "vier" -- German for four -- in bubble-style letters.

The tag, or signature, has appeared in Walton Street, Jericho, and on a derelict building on the St Thomas School site off Hollybush Row.

Pc Paul Phillips, who last year spearheaded a crackdown on graffiti in Oxford with city councillor Paul Sargent, is appealing for help to catch the offender.

He said: "Someone must know who is displaying that tag. We urge them to come forward and tell us in confidence.

"It started off as small tags but as the person gets more confident the tags are getting bigger and more high profile.

"It is antisocial behaviour. Graffiti degrades residential areas and places of interest and we are keen to put a stop to it."

Malcolm Hart, streetscene officer for Oxford City Council's City Works cleansing department, said more than £30,000 was spent cleaning up graffiti tags every year using the latest steam cleaning equipment.

He said: "Graffiti is a criminal offence and it should be reported to the police."

The city council is only allowed to scrub graffiti from public buildings. It has to be given permission by the landowner to remove it from non-council property.

Graffiti can be reported to the council on 01865 252900 or Oxford police on 08458 505505 or Crimestoppers anonymously on 0800 555111.