A prison officer's neck has been slashed by an inmate at HMP Altcourse prison in Liverpool.
The man was attacked with a razor shortly before 4:20pm on Wednesday and was rushed to hospital, Merseyside Police said.
A spokeswoman for the force said: "An investigation into the full circumstances of the incident is on-going".
The attack took place in the segregation area of the prison as the inmate was due to be transferred to a Category A prison.
The unnamed prisoner, who had been charged with murder, is believed to have attacked the officer with a razor he hid during his shower and shave while he was being transferred from the prison.
The director for HMP Altcourse, Steve Williams, said: “A member of our team at HMP Altcourse was attacked by a prisoner and was taken to hospital by ambulance.
"We are working closely with Merseyside Police and supporting their investigation into this incident and we continue to support the officer and his family.
"There is no place in our prison community for violent behaviour and we will always work with the police to push for the strongest possible sanctions in court against prisoners who undermine safety."
The officer has since been discharged from hospital.