Two people were injured in the epicenter of Visso, where the rubble of collapsed buildings tumbled into the streets. But the Civil Protection agency had no other immediate reports of injuries or deaths.
The first quake carried a magnitude of 5.4, but the second one was eight times stronger at 6.1, according to the U.S. Geological Survey.
"It was an unheard-of violence. Many houses collapsed," Ussita Mayor Marco Rinaldi told Sky TG24. "The facade of the church collapsed. By now I have felt many earthquakes. This is the strongest of my life. It was something terrible."
Calling it "apocalyptic," he said: "People are screaming on the street and now we are without lights."
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. Schools were closed in several towns Thursday as a precaution.
"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 first 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, 170 kilometers northeast of Rome, and said it had a depth of some 10 kilometers (six miles).
The second aftershock struck two hours later at 9:18 p.m. with a similar depth.
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 Wednesday's aftershocks but "We are thanking God that there are no dead and no injured."
The original Aug. 24 6.2-magnitude quake was still 41 percent stronger than even the second aftershock.
Wednesday's temblors were 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 Tronto, Aleandro Petrucci, said the aftershocks felt stronger than the August quake, 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 quakes were actually aftershocks of the magnitude 6.2 earthquake from two months ago. Because they were 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 quakes, the USGS estimates that about 24 million people likely felt at least weak shaking.
This original quake was 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.
AP writer Colleen Barry contributed from Milan and AP science writer Seth Borenstein contributed from Washington.
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