Rock and country star Steve Earle surprised Oxford fans by telling them he had buried the ashes of a convicted killer near the city.

During his packed show at the Carling Academy Oxford, in Cowley Road, on Saturday, the US star said he had visited the city only once before.

He explained it was to bury the remains of death row inmate Jonathan Nobleswho was executed by lethal injection in 1998.

Mr Earle said he buried the ashes "somewhat illegally out towards Woodstock", but did not disclose the exact location.

The Academy crowd listened in near silence as Earle talked of Nobles, but erupted into a cheer as he explained that the double murderer had wanted to be buried where there was no capital punishment.

Award-winning singer-songwriter Earle, whose hits include Copperhead Road, I Feel Alright and I Ain't Never Satisfied, met Nobles as he started working against the death penalty in the early 1990s.

Nobles 37, was convicted of the 1986 murders of Mitzi Johnson Nalley, 21, and Kelly Farquhar, 24, in Austin, Texas.

Mr Earle, 53, who wrote music for death row film Dead Man Walking, was a witness at Nobles' execution, which took place in Texas, where the then-governor was George W Bush.

He said: "It is terrifying. It is torture. It was for me. I do not think I will ever recover from it. I have absolute waking nightmares about it."

He said Nobles' ashes had sat on his mantelpiece for more than a year before he decided where to bury them.

Mr Earle also wrote a song about the execution called Over Yonder (Jonathan's Song).

Seven-times married Mr Earle, who has spent time in jail on drugs and firearms charges, was in Oxford as part of a European tour with his wife, singer-songwriter Alison Moorer.

Now based in New York, he is known as a political activist.

The whereabouts of the ashes will remain a mystery. Woodstock Town Council clerk Peter Anderson said: "I am not aware of a policy as to where ashes can be buried. I have never been asked that question.

"The only approaches I have had have been about interment of ashes at the Woodstock Lawn Cemetery."

Ashes can legally be scattered anywhere associated with the deceased, provided the owners of the land or appropriate authority give permission.

This can include the sea, at a football ground, in a private garden, or at any spot which has personal connections with the person who died. However, burying ashes is permitted only within the grounds of a crematorium, in a churchyard, in a grave, or in someone's own garden.