A 60kg device was found in a car in the Derrylin Road area of Fermanagh at the weekend. It was defused on Saturday and taken for further examination.
Senior officers believed the bomb was headed for the nearby Lisnaskea Police Station, but in a statement to UTV, which claims to be from ONH, said the target was the Lough Erne resort.
In June, some of the world's most powerful leaders will meet at the hotel for the summit - just 16 miles from where the device was discovered.
Using a codeword, ONH also stated they were responsible for a foiled mortar-type bomb attack on a police station in Belfast earlier this month.
The group also released images of the device, which sparked a security alert lasting almost 24 hours.
The caption with the image states: 'MK1 10KG mortar, Range 300 meters'.
An off-duty police officer spotted the potentially deadly device on the Ballygomartin Road on Friday, 15 March.