The deceased has been identified as Santosh Kumar, a hosiery items vendor in Sarojini Nagar market, they said.
The incident came to light around 5.45 AM when Kumar's cousin cum roommate Sonu came home and saw him lying in a pool of blood on the terrace outside his room. He raised an alarm and the neighbour rushed there, a senior official said.
From preliminary investigation, it emerged that unidentified assailants had gagged him with a cloth and then slit his throat with a sharp weapon, he said, adding they also smashed his face with a heavy object or by beating repeatedly by fists.
Sonu and a neighbour, who called up the police but went missing after that are under the scanner, he added.
