Four Wormwood Scrubs prisoners have been arrested over the fatal stabbing of another inmate, Scotland Yard has said.
Police were called at 3.19pm on Wednesday to reports a man had suffered stab injuries at the jail.
They rushed there with the ambulance service but he died at the scene.
The Metropolitan Police said his next of kin had been informed but they were still waiting for formal identification.
They believe he is deceased is 25-year-old Saleh Khader.
Four inmates - two 21-year-old men, one aged 20 and another aged 23 - have been arrested on suspicion of murder. They are in police custody.
A post-mortem will take place “in due course”, the Met said.