A 27-year-old man was bludgeoned to death by a 13-year old in northeast Delhi's Sonia Vihar. The victim was identified as Saabir.
Police said the nephew of the victim and the juvenile had had an altercation on July 7.
"Saabir's nephew and the accused juvenile had a scuffle over a minor issue. Saabir's family members were taking the accused to his house to lodge a complaint with his parents when he ran away before returning with a wooden plank which had nails on it and attacked Saabir on the head with it," said an officer.
A case of attempt to murder was registered on the statement of the neighbours and family members, while Saabir was taken to the Guru Teg Bahadur Hospital in a critical state. He succumbed to his injuries on Wednesday morning.
The juvenile has been sent to a fortnight's custody.
Meanwhile, in another incident, the headless body of a 35-year-old man was found near a temple in southwest Delhi's Najafgarh early on Wednesday morning. Police said the severed head of the victim was found dumped a few metres away.
The identity of the victim could be established only after police recovered the head. He was identified as Sanjay Kumar, who worked as a labourer and had been living in Nazafgarh area for some years.
A senior police officer said the incident came to light around 7.30am when a passerby discovered the headless body near Sai Baba temple and called the police control room.
"A police team reached the spot and during inspection found the head of the victim a few metres from the body," said a police officer, adding the victim's body was sent to a government hospital for post-mortem examination.
"The reason behind Kumar's murder is yet to be ascertained. Prima facie we suspect involvement of more than one person in the brutal killing. A case of murder has been registered and investigations are underway," the officer added.