ROME — An earthquake, believed to be the strongest to hit Italy since 1980, struck the center of the country on Sunday, four days after two back-to-back quakes severely damaged buildings and left thousands homeless in the area. The temblor on Sunday also caused fresh damage to the towns destroyed by a quake that killed nearly 300 people in August.

The quake, which had a magnitude of 6.5, according to Italy’s national geophysical and volcanology institute, struck at 7:41 a.m. with its epicenter near Norcia. It was felt as far away as Bolzano in northern Italy and Puglia in the south, according to Italian news reports.

Most of the towns in the area had already been evacuated after the recent seismic activity, so there were no immediate reports of deaths.

About 20 people were injured but none killed, said Fabrizio Curcio, the head of Italy’s civil protection department. “It was an important earthquake,” he said.