He said Ms Duritskaya had been told to remain in Moscow until mid-week, but that she was upset to be kept under armed guard.
“She is ready to come back to Russia if need be, but investigators don’t want to let her go. As a witness, she is not denied the freedom of movement but actually she is under home arrest.”
He said Ms Duritskaya had “categorically refused” to accept the bodyguards provided by investigators.
“Despite this fact, two to four men are accompanying her. More men are standing guard at her apartment,” he said.
The Russian Investigative Committee, which is probing the murder, said that she was a key witness and that detectives “have reasons to conduct additional investigative actions with her”.
But Mr Prokhorov said Ms Duritskaya had given “all the necessary witness accounts”, and was seeking help from the Ukrainian consul to be allowed to return to her homeland.
Tens of thousands of people marched in protest at the murder in Moscow yesterday, with a further 6,000 protesting in St Petersburg.