The girl, daughter of a labourer, had gone to a shop at a short distance from her house in Bhikampur locality on Tuesday but did not return home, police said.
As her family launched a search, they recovered the mutilated body of the girl who also appeared to have been sexually assaulted, police said.
A manhunt was launched for the accused and police zeroed in on one Arvind (32), a former employee of the shop where the girl had gone.
As he was being brought to the police station, a group of locals attacked him, police said.
He was admitted to the Jawaharlal Nehru Medical College Hospital with multiple injuries, where he succumbed last night.
A case of murder has been lodged against 200 unnamed persons in this connection, police added.
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