A 17-year-old girl was found murdered at her house in Rohini's Begumpur area, the police said on Saturday.
A 25-year-old man identified as Laik Khan is the main suspect and is missing, they said.
"The victim was allegedly killed by Laik Khan," senior police official (Rohini) PK Mishra said.
Prima facie the reason behind the crime appears to be the victim's refusal to marry the accused, the police said.
They said the incident took place on Friday and police received information about it around 9.30 pm from the hospital.
According to police, the person who died earlier used to live with her family in Bawana area. They had good relations with their neighbours. However, they shifted to Begumpur area around one year ago.
Laik, who was their neighbour earlier, used to visit them often at their new home. He came to visit them on Friday also and had a plan to have dinner with them, the police said.
The victim's brother and cousin went out to buy some grocery items. When they returned, they saw Laik locking the house and rushing out of the area.
They initially thought that Neetu had also gone with him and waited outside the house. When Neetu's mother came home, she called her on her mobile phone which was ringing inside the locked house.
They broke open the door and found her lying in a pool of blood with a head injury, a senior police officer said.
The victim was rushed to a nearby hospital where she was declared brought dead. She had sustained a head injury caused by a hammer, the officer said.
During investigation, Neetu's cousin brother said he suspected that Laik might have proposed to her for marriage when no one was around. When she refused, he seemed to have attacked her with a hammer and fled from the spot, police said.
Mr Mishra said the accused works in a factory and lives with his uncle in Bawana area. He is currently missing. Police are trying to arrest him and further investigation is underway.
The victim's parents work at a factory manufacturing car floor mats, they said.
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