An earthquake of magnitude 6.4 struck 68 km east of the central Italian city of Perugia at 1918 GMT on Wednesday, the United States Geological Survey said, the second of the evening whose tremors were felt as far away as the capital Rome.
The quakes came two months after almost 300 people were killed in the region by a quake that levelled several small towns.
The first quake of 5.4-magnitude struck central Italy 122 kilometres north-east of Rome, the European Mediterranean Seismological Centre said.
Two people were injured in the Visso area near the quake epicenter, but otherwise there were no other immediate reports of victims, said Italy's civil protection chief, Fabrizio Curcio. Old churches crumbled and other buildings were damaged, though many of them were in zones that were declared off-limits after the Aug. 24 quake that flattened parts of three towns.
"We're without power, waiting for emergency crews," said Mauro Falcucci, the mayor of Castelsantangelo sul Nera, near the epicenter. Speaking to Sky TG24, he said: "We can't see anything. It's tough. Really tough."
He said some buildings had collapsed, but that there were no immediate reports of injuries in his community. He added that darkness and a downpour were impeding a full accounting.
Italy's national vulcanology center said the quake struck at 7:10 p.m. local time (1710 GMT) with an epicenter in the Macerata area, near Perugia in the quake-prone Apennine Mountain chain. The U.S. Geological Survey put the epicenter near Visso and said it had a depth of some 10 kilometers (six miles).
Experts say even relatively modest quakes that have shallow depths can cause significant damage because the seismic waves are closer to the surface. But seismologist Gianluca Valensise said a 10-kilometer depth is within the norm for an Apennine temblor.
The Aug. 24 quake destroyed the hilltop village of Amatrice and other nearby towns and had a depth of about 10 kilometers. Amatrice Mayor Sergio Pirozzi said residents felt the quake, but "We are thanking God that there are no dead and no injured."
Wednesday's quake was felt from Perugia in Umbria to the capital Rome to the central Italian town of L'Aquila, which was struck by a deadly quake in 2009. The mayor of L'Aquila, however, said there were no immediate reports of damage there.
A section of a major state highway north of Rome, the Salaria, was closed near Arquata del Tronto as a precaution because of a quake-induced landslide, said a spokeswoman for the civil protection agency, Ornella De Luca.
The mayor of Arquata del Tronco, Aleandro Petrucci, said the quake felt stronger than the August temblor, which devastated parts of his town. But he said there were no reports of injuries to date and that the zone hardest hit by the last quake remained uninhabitable.
"We don't worry because there is no one in the red zone, if something fell, walls fell," he said.
In Rome, some 230 kilometers (145 miles) southwest from the epicenter, centuries-old palazzi shook and officials at the Foreign Ministry evacuated the building.
The quake was actually an aftershock of the magnitude 6.2 earthquake from two months ago. Because it was so close to the surface, it has the potential to cause more shaking and more damage, "coupled with infrastructure that's vulnerable to shaking," said U.S. Geological Survey seismologist Paul Earle.
"They have a lot of old buildings that weren't constructed at a time with modern seismic codes," he said.
Given the size, depth and location of the quake, the USGS estimates that about 12 million people likely felt at least weak shaking.
This quake is about 20 kilometers (12 miles) northwest of the original shock, which puts it on the northern edge of the aftershock sequence and two months is normal for aftershocks, Earle said. The August 6.2 quake was five times bigger than Wednesday's and was 11 times stronger based on energy released.
Seismologists initially thought this aftershock was magnitude 5.4 but the USGS upgraded it to 5.5 when they checked its waves and that estimate may still change, Earle said.
