Fabrizio Curcio, the head of Italy's civil protection service, classed the quake as "severe". The shocks were strong enough to wake residents of central Rome, some 150 kilometers (90 miles) away.
The worst damage was suffered by Pescara del Tronto, a hamlet near Arquata in the Marche region which civil protection workers described as having been virtually razed.
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Ten bodies had been recovered there by mid-morning and rescuers were braced for further fatalities.
Aleandro Petrucci, the mayor of Arquata, said Pescara had "just completely disintegrated."
Another two people died and a family of four including two young children were trapped, feared dead, in their collapsed house in Accumoli, according to its mayor Stefano Petrucci.
"We have a tragedy here," said Petrucci. "There are people under the ruins, it is not a good situation."
Gastronomic Beauty Spot
A village resident told Rai television that she had been woken by the shaking in time to witness the wall of her bedroom cracking open. She was able to escape into the street with her children.
In Amatrice, the president of the Lazio region confirmed six bodies had been recovered.
The village was packed with visitors at the peak of the summer season when the quake struck, destroying the picturesque hilltop village's main street.
The mayor said difficult access to the village had prevented emergency services getting through.
"There is a landslide on one road, a bridge is about to collapse on the other one," he said. "We can hear voices under the rubble."
Amatrice is famous in Italy as a beauty spot and is a popular holiday destination for Romans seeking cool mountain air at the height of the summer.
The first quake struck shortly after 3.30 am (0130 GMT), according to the United States Geological Survey, and a 5.4-magnitude aftershock followed an hour later.
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USGS's PAGER system, which predicts the impact of earthquakes, issued a red alert -- suggesting significant casualties and damage based on previous quake data.
In 2009, a 6.3-magnitude earthquake struck close to the university city of Aquila in the Abruzzo region and left more than 300 people dead.
That disaster led to lengthy recriminations over lax building controls and the failure of authorities to warn residents that a quake could be imminent.
Italy is often shaken by earthquakes, usually centered on the mountainous spine of the boot-shaped country.
Another quake hit the northern Emilia Romagna region in May 2012, when two violent shocks 10 days apart left 23 people dead and 14,000 others homeless.