The three inmates of high-security ward of Jail number 1 of Tihar--Ishwar, Vijay and Shadab were being taken back to their ward from the jail dispensary yesterday when they were attacked by three other prisoners Anil, Vasu and Sandeep.
Anil was rushed to Deen Dayal Upadhyay Hospital where he succumbed to the injuries last evening, said Mukesh Prasad, Additional Inspector General of Tihar.
The other prisoner, Ishwar, was rushed to the DDU Hospital where he was operated upon but could not be saved.
The prisoners involved in the clash have multiple criminal cases against them, officials said.
The exact reason behind the clash will be known after inquiry by jail authorities, they said.