Dozens of buildings collapsed in communities close to the epicentre of the quake in a remote area straddling the regions of Umbria, Marche and Lazio.
Deaths were reported in the villages of Amatrice, Accumoli and Arquata del Tronto as residents and emergency services scrambled frantically to rescue people trapped beneath the ruins of houses reduced to piles of masonry.
It was Italy’s most powerful earthquake since 2009, when more than 300 people died in and around the city of Aquila, just to the south of where today’s quake struck.
“The situation is dramatic, there are many dead. I cannot give a toll for now because rescue efforts are under way and it is very, very difficult,” said Amatrice mayor Sergio Pirozzi.
“Half the village has disappeared.”
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 kilometres away.
The first two confirmed victims were an elderly couple whose home collapsed in Pescara del Tronto, a hamlet near Arquata in the Marche region.
Aleandro Petrucci, the mayor of Arquata, said Pescara was one of “two or three hamlets that have 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.”
A resident of the village 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.
Amatrice, where the local authorities confirmed five deaths, was packed with visitors at the peak of the summer season when the quake struck, destroying the hilltop village’s main street.
Mayor Pirozzi 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 3.30am (8:30am Thai time), according to the United States Geological Survey, and a 5.4-magnitude aftershock followed an hour later.
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 centred 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.