The aftershock hit at 6.28am, Italy's national geological insititute said. It was preceded by several smaller tremors overnight in the Rieti province, and followed by several more within the following hour.
Amatrice normally has a population of around 2,500 but it was packed with visitors when the quake struck as people slept in the early hours of Wednesday. Some 500 tremors have been felt since.
Rescuers were continuing their search for bodies on Friday morning.