The claim came from a victim support campaigner after two more patients lodged release applications.

The appeals follow the highly-publicised case of Noel Ruddle, who gained freedom after successfully arguing that his mental condition had changed and treatment programmes were no longer appropriate.

A spokesman for Carstairs Hospital said the new cases bore no resemblance to the Ruddle affair.

The spokesman confirmed the pair - believed to be Brian Docherty and Karl Anderson - had been detained at the hospital.

Patients 'entitled' to appeal

Like Ruddle, the fresh appeals lodged at Lanark Sheriff Court on 17 August, involve criminals sent to Carstairs without limit of time.

The hospital spokesman said: "Patients are entitled to appeal against detention at the state hospital.

Ruddle's release caused public outrage

"We are confident both cases will not succeed."

Director of the Victims of Crime Trust, Norman Brennan, said it was the government's responsibility to protect society from such people.

"These people really are like unexploded World War Two bombs that haven't been detonated.

"There is a chance that it will not happen and it will remain dormant but there is still a risk that it will go off, or he will go off as it is in this case and that someone else will lose their lives.

"The government is absolutely responsible to protect those in society that are vulnerable to such killers."

'Urgent matter'

The SNP's justice spokeswoman Roseanna Cunningham said: "This is a matter of urgency for the Scottish Executive because we cannot allow more dangerous people out onto the streets."

Roseanna Cunningham: "Executive must act"

Scotland's First Minister Donald Dewar revealed the new cases in a written reply to a member of the Scottish Parliament on Thursday.

Mr Dewar is opposing the new appeals and at least one of the cases will come before Sheriff John Douglas Allan - who granted freedom to Ruddle.

Ruddle - who shot dead neighbour James McConville, 33, with a Kalashnikov rifle - was backed in his bid for freedom from Carstairs by its board of management because he developed a personality disorder which the hospital could not treat.

The 44-year-old was diagnosed as a paranoid schizophrenic when he was convicted of the crime in 1992.

But within 10 months of specialised drug treatment his paranoia eased and he was left with a violent and anti-social personality disorder.

Reid case

Last year, the House of Lords rejected a bid for freedom by Carstairs inmate Alexander Reid.

Reid was ordered to be detained without limit of time for stabbing to death Angela McCabe in her Glasgow home in 1967.

His plea of culpable homicide was accepted because of his mental state.

When Ruddle was released at the beginning of August, politicians expressed fears there would be a deluge of prisoners held under the Mental Health Act (Scotland) making bids for freedom.