In a coded message to The Guardian newspaper in London, Oglaigh Na hEireann also claimed responsibility for a thwarted attempt to attack a police station with a mortar on March 15. The statement was signed "Oglaigh Na hEireann (ONH) Belfast" and included photographs of the mortar.
Police originally believed the bomb was intended for a nearby police station but the statement linked it to the Group of Eight summit.
"Car bomb defused in County Fermanagh on Sat 23rd March," the statement said. "Target was hotel hosting G8 summit in June. Photos are of mortar bomb deployed in Belfast on March 15."
Oglaigh na hEireann, which can be translated as "soldiers of Ireland," was first used for the Irish Volunteers, formed in 1913, and then adopted as the name for the newly formed Irish army after independence. The name has been used over the decades by republican groups claiming to be the real heirs of the rebels who fought for independence.
The bomb was discovered in an abandoned car in County Fermanagh. The county is home to the Lough Erne Hotel & Golf Resort, where U.S. President Barack Obama, President Vladimir Putin of Russia, British Prime Minister David Cameron, French President Francois Hollande and other world leaders are scheduled to meet in June.