At least 37 people have died in the magnitude 6 earthquake that struck central Italy, according to Italy's civil protection agency.
The agency, which is coordinating the rescue effort, gave the preliminary toll as rescue teams continued to claw through debris in hard-hit towns.
'The town isn't here anymore,' said Sergio Pirozzi, the mayor of Amatrice.
The quake struck at 3.36am local time and was felt across a broad swath of central Italy, including Rome, where residents felt a long swaying followed by aftershocks. The temblor was felt from the Lazio region into Umbria and Le Marche on the Adriatic coast.
The hardest-hit towns were Amatrice, Accumoli near Rieti, some 80 miles north-east of Rome, and Pescara del Tronto further east.
The centre of Amatrice was devastated, with entire buildings razed and the air thick with dust and smelling strongly of gas.
Rocks and metal tumbled onto the streets and dazed residents huddled in piazzas as some 39 aftershocks jolted the region into the early morning hours, some as strong as 5.1.
'The whole ceiling fell but did not hit me,' marvelled resident Maria Gianni. 'I just managed to put a pillow on my head and I wasn't hit luckily, just slightly injured my leg.'
Another woman, sitting in front of her destroyed home with a blanket over her shoulders, said she did not know what had become of her loved ones.
'It was one of the most beautiful towns of Italy and now there's nothing left,' she said. 'I don't know what we'll do.'
As daylight dawned, residents, civil protection workers and even priests began digging out with shovels, bulldozers and their bare hands, trying to reach survivors. There was relief as a woman was pulled out alive from one building, followed by a dog.
'We need chainsaws, shears to cut iron bars, and jacks to remove beams: everything, we need everything,' civil protection worker Andrea Gentili told The Associated Press. Italy's national blood drive association appealed for donations to Rieti's hospital.
The devastation harked back to the 2009 quake that killed more than 300 people in and around L'Aquila, about 55 miles south of the latest quake. The town sent emergency teams on Wednesday to help with the rescue.
'I don't know what to say. We are living this immense tragedy,' said the Reverend Savino D'Amelio, a parish priest in Amatrice. 'We are only hoping there will be the least number of victims possible and that we all have the courage to move on.'
Another hard-hit town was Pescara del Tronto, in the Le Marche region, where the main road was covered in debris.
Residents were digging their neighbours out by hand since emergency crews had not yet arrived in force. Photos taken from the air by regional firefighters showed the town essentially flattened.
'There are broken liquor bottles all over the place,' said Gino Petrucci, owner of a bar in nearby Arquata Del Tronto where he was beginning the clean-up.
The Italian geological service put the magnitude at 6.0; the US Geological Survey reported 6.2 with the epicentre at Norcia, about 105 miles north-east of Rome, and with a relatively shallow depth of 6 miles.
'Quakes with this magnitude at this depth in our territory in general create building collapses, which can result in deaths,' said the head of Italy's civil protection service, Fabrizio Curcio. He added that the region is popular with tourists escaping the heat of Rome, with more residents than at other times of the year, and that a single building collapse could raise the toll significantly.
In Amatrice, the Reverend Fabio Gammarota, priest of a nearby parish, said he had blessed seven bodies extracted so far. 'One was a friend of mine,' he said.
Mr Pirozzi estimated dozens of residents were buried under collapsed buildings and that heavy equipment was needed to clear streets clogged with debris.
Prime Minister Matteo Renzi's office tweeted that heavy equipment was arriving.
A 1997 quake killed a dozen people in the area and severely damaged one of the jewels of Umbria, the Basilica of St Francis in Assisi, filled with Giotto frescoes.
Pope Francis skipped his traditional catechism for his general audience and instead invited pilgrims in St Peter's Square to recite the rosary with him.
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