The brother later surrendered before the police.
According to Doghat police station official, the girl was having an affair with a youth of neighbouring village for the past sometime and her family had raised serious objections over it.
The girl, who eloped with the youth on Saturday, was brought back by her father and brother yesterday and today morning while she was sleeping, her brother strangulated her to death, police said.
The brother later surrendered before the police saying that the family was "facing embarrassment" in the village because of the relationship and he had "no regrets" for taking the extreme step.