Police have received reports that a man wanted in connection with a murder in Londonderry is at large in the city.
The detective leading the investigation into the shooting of Barry McCrory, 35, said "unconfirmed sightings" of 58-year-old Kieran McLaughlin have been reported in the Derry area.
Detective Chief Inspector Ian Harrison's warning comes after a major operation was mounted by armed officers across the border in Co Donegal.
Gardai surrounded a house in the Burnfoot area through last night believing that Mr McLaughlin was holed up inside. But the operation was stood down in the early hours when they established that the property was empty.
Burnfoot is only a short distance from Londonderry, around five miles (8 km) across the border.
Mr McCrory was gunned down in a flat in Derry city centre on Thursday morning.
His partner, who was in the Shipquay Street property at the time, was bundled into another room by the lone killer before the fatal shots were fired.
Mr Harrison repeated a previous warning to the public not to approach Mr McLaughlin.
"We are continuing to appeal to the public for their assistance in establishing the current whereabouts of 58-year-old Kieran McLaughlin," he said.
"I can confirm there have been a number unconfirmed sightings of Mr McLaughlin in the Derry area but it is imperative that future sightings of Kieran are reported to police immediately and reiterate to the public not to approach him, but to contact police on 999 if you think you know of his whereabouts.
"I would also emphasise to Kieran to contact police immediately as we are actively seeking to speak with you. It is our wish that this matter is resolved without further incident."
Mr McLaughlin is 5ft 7in, of medium build with blue eyes and grey hair.
It is understood the murder of Mr McCrory relates to a fallout over alleged criminality.
The victim was known to police for previous offending.
The murder took place less than 24 hours after the body of a father-of-four was found in a lake in north Belfast.
It was understood Kevin Kearney, 46, was shot dead by dissident republicans. But a 39-year-old man arrested in connection with the shooting yesterday was released today without charge.
Officers say they are not linking the two murders at this stage.