'I'm innocent': Meredith Kercher killer speaks for first time

The American student was found guilty along with Italian former boyfriend Raffaele Sollecito in December of killing Miss Kercher but said she will "fight to prove" she is innocent.

She also revealed she exchanges letters with 26-year-old Sollecito, who is being held in a different prison.

Knox, 23, said: "We often write to each other, we give each other strength.

"We have ended up in a surreal affair that we still don't understand but at least it unites us. The affection remains from the love we had."

In an interview with Italian glossy magazine Oggi, Knox described her prison routine, saying she gets up at around 6am and practises yoga before replying to the 300 letters she receives each month from family, friends and supporters.

The University of Washington student often spends the afternoons studying and playing volleyball with other inmates.

She insisted she was not involved in Miss Kercher's murder, adding: "I find it really hard to accept that my friend Meredith is dead, and I am accused of killing her. It's really hard for me and, at times, the whole thing is much bigger than me."

Miss Kercher, 21, from Coulsdon, Surrey, was found dead in her bedroom in Perugia on November 2, 2007 in the house she lived in with Knox and others on her year abroad in the Umbrian town.

Her throat had been slit and her semi-naked body was partially covered by a duvet.

Knox, from Seattle, was jailed for 26 years while Sollecito was sentenced to 25 years.

A third defendant, Rudy Hermann Guede, an immigrant from the Ivory Coast, was convicted of Miss Kercher's murder in a separate trial. His 30-year prison sentence was later reduced to 16 years on appeal.

A claim by Mafia informant Luciano Aviello that he has evidence Miss Kercher was killed by his brother, Antonio, will form part of an appeal by Knox's defence team.

She said: "When all my cellmates heard the news they hugged me and said: 'Now you will be freed'.

"I kept calm because the greatest danger is getting hopeful and of believing too much in freedom."