A memorial to a murdered policeman in Leeds has been vandalised in the second attack of its type in a month.
In the latest incident, someone tried to set fire to a memorial stone marking the place where Pc Ian Broadhurst was shot dead on Boxing Day 2003.
Police said the "despicable" attack took place on Sunday night.
Two men were arrested in November after a swastika was daubed on a memorial stone in Kirkgate where Sgt John Speed was killed in October 1984.
West Yorkshire Police said the two incidents were not believed to be linked.
A force spokesman said Pc Broadhurst's memorial was left "blackened" between Sunday evening and Monday morning after someone ignited an accelerant which had been poured over it.
Traffic officer Pc Broadhurst, 34, was shot by former US Marine David Bieber near the junction of Dib Lane and Grange Park Avenue in the Fearnville area of Leeds.
Bieber, 42, was found guilty of murder in 2004 and jailed for life with a recommendation he should never be released.
In 2008, Appeal Court judges said Bieber should serve a minimum of 37 years in prison before being considered for parole.
Ch Supt Richard Jackson, the divisional commander for North East Leeds, said: "Police officers go to work every day never knowing what could happen and thankfully few never make the ultimate sacrifice made by Ian Broadhurst.
"The memorial is a way for local people, local officers and Ian's friends and family to mark the terrible events of December 26, 2003 and for someone to deliberately vandalise the memorial is about as despicable as it's possible to get.
"I would ask the local community to come forward with any information they may have on those responsible so we can ensure they are brought to justice."