Murder suspect Amanda Knox threatened a man with a knife just 24 hours before the body of a British student was found murdered, a new witness claimed today.

An Albanian has told police and prosecutors that Knox, 20, was with her boyfriend and fellow suspect Raffaele Sollecito, 24, when the terrifying incident took place.

He said that he was parking close to the house murder victim Meredith Kercher, 20, shared with Knox - who called herself Foxy Knoxy - when his car nudged a waste container.

He claims this provoked an argument with Knox, who eventually pulled a knife on him.

Police in Perugia are investigating the November 1 murder of Meredith, who was found semi-naked in a blood-spattered apartment, having apparently been the victim of a violent sexual assault.

The unidentified witness said: "I've only come forward now because I was scared.

"I spoke with a lawyer before coming to see you but in the end I realized it was important.

"The evening of 31st October I arrived in my car close to the house on Via della Pergola.

"As I was parking my car I hit a rubbish dumpster - a second later I saw two people, a man and a woman, who were behind it and they came towards me shouting.

"We started arguing and then all of a sudden the girl pulled out a knife, she was shouting at me and pointing it at me.

"I am certain it was Amanda Knox, with her was Raffaele Sollecito.

"Then out of the darkness emerged another man, it was Rudy, the three of them were together."

The sensational new evidence was being kept secret but was leaked and today prosecutor Giuliano Mignini said: "This is a very serious matter.

"This statement was a secret and now it is in the public domain. I am not prepared to say anything else about it."

Police sources however said that particulars of his statement including the fact it had been raining that night had already been checked and proved correct.

A source close to the investigation added: "He is a Albanian with a regular residents permit and he has no record.

"His story is being taken seriously as it proves that all three suspects knew each other.

"Knox and Sollecito have denied knowing Rudy but this man's statement puts them together and with a knife 24 hours before poor Meredith was murdered.

"It also suggests that the three were out there armed with a knife and already planning this murder when they were disturbed and it was put back a day.

"He is being taken as a serious and credible witness."