The fire began at the Surf Hotel in Hampton Beach just before 12:01 a.m. and spread quickly after winds clocked at 60 mph blew off the roof of the building, WMUR-TV in Hampton Beach reports.
Crews from Maine and Massachusetts were among the 125 firefighters called in to battle the blaze.
Fire chief Chris Silver of Hampton declared the fire contained but not completely out.
There were no immediate reports of any injuries and no information on the cause of the fire or the extent of damage to the buildings involved.
Silver said four fires have broken out on the same block in the past 100 years.
The Surf Hotel is located on Ocean Boulevard across the street from the beach.