ROME (AFP) - Rome police were stumped on Wednesday after the discovery of a severed leg tattooed with the phrase "a good day to die".

"A passerby rang the police yesterday afternoon to inform us that they had found a severed leg," police in Rome told AFP.

The leg, discovered on Tuesday near the Tiber river in the north of the capital, is severed below the knee and sports various tattoos including the words "a good day to die" and a football slogan supporting one of Rome's teams, Lazio.

Investigators believe the limb belongs to a man in his 40s, and are not ruling out the possibility other body parts could be found, media reports said.

Not yet in a state of decomposition, the limb was being examined by forensic doctors at the Gemelli hospital in Rome, the reports said.