A man assaulted outside a bar in Toomebridge has died.
James McDonagh, 28, from Castledawson was attacked outside the Elk Inn on the Hillhead Road in the early hours of Sunday morning.
He died in the Royal Victoria Hospital Belfast on Monday, police said.
Three men aged 52, 24 and 20 who were arrested late last night in the Toomebridge area remain in custody in a Belfast police station.
Detectives from PSNI Serious Crime Branch have launched a murder investigation.
The officer leading the investigation, Detective Chief Inspector Eamonn Corrigan, said: "It was reported that at around 2am on Sunday morning an altercation took place outside the Elk Inn."
He appealed for anyone who witnessed the incident or with information which could assist the investigation to contact the police incident room at Magherafelt or charity Crimestoppers.