Four teenagers have been arrested in connection with the death of a 40-year-old man in a town centre, police said.
The boys, three aged 15 and one aged 16, are in custody where they will be questioned by officers following the death of the man in Worksop on Saturday night.
The arrests follow reports of an assault at around 7.30pm in Bridge Street, near its junction with Central Avenue and Ryton Street, police said.
The victim was taken to Bassetlaw District Hospital where he was pronounced dead.
A statement from Nottinghamshire Police said: "A murder inquiry is now under way.
"Formal identification of the victim has yet to take place and a post-mortem examination is due to be conducted to establish the cause of death.
"Four boys, three aged 15 and one aged 16, remain in custody where they will be questioned by officers today.
"A cordon is in place at the scene while forensic enquiries are carried out."
Nottinghamshire Police said they were appealing for witnesses to the incident.